origin of lag in lcd displays manufacturer

Display lag is a phenomenon associated with most types of liquid crystal displays (LCDs) like smartphones and computers and nearly all types of high-definition televisions (HDTVs). It refers to latency, or lag between when the signal is sent to the display and when the display starts to show that signal. This lag time has been measured as high as 68 ms,Hz display. Display lag is not to be confused with pixel response time, which is the amount of time it takes for a pixel to change from one brightness value to another. Currently the majority of manufacturers quote the pixel response time, but neglect to report display lag.

For older analog cathode ray tube (CRT) technology, display lag is nearly zero, due to the nature of the technology, which does not have the ability to store image data before display. The picture signal is minimally processed internally, simply for demodulation from a radio-frequency (RF) carrier wave (for televisions), and then splitting into separate signals for the red, green, and blue electron guns, and for the timing of the vertical and horizontal sync. Image adjustments typically involve reshaping the signal waveform but without storage, so the image is written to the screen as fast as it is received, with only nanoseconds of delay for the signal to traverse the wiring inside the device from input to the screen.

For modern digital signals, significant computer processing power and memory storage is needed to prepare an input signal for display. For either over-the-air or cable TV, the same analog demodulation techniques are used, but after that, then the signal is converted to digital data, which must be decompressed using the MPEG codec, and rendered into an image bitmap stored in a frame buffer.

For progressive scan display modes, the signal processing stops here, and the frame buffer is immediately written to the display device. In its simplest form, this processing may take several microseconds to occur.

For interlaced video, additional processing is frequently applied to deinterlace the image and make it seem to be clearer or more detailed than it actually is. This is done by storing several interlaced frames and then applying algorithms to determine areas of motion and stillness, and to either merge interlaced frames for smoothing or extrapolate where pixels are in motion, the resulting calculated frame buffer is then written to the display device.

De-interlacing imposes a delay that can be no shorter than the number of frames being stored for reference, plus an additional variable period for calculating the resulting extrapolated frame buffer; delays of 16-32ms are common.

While the pixel response time of the display is usually listed in the monitor"s specifications, no manufacturers advertise the display lag of their displays, likely because the trend has been to increase display lag as manufacturers find more ways to process input at the display level before it is shown. Possible culprits are the processing overhead of HDCP, Digital Rights Management (DRM), and also DSP techniques employed to reduce the effects of ghosting – and the cause may vary depending on the model of display. Investigations have been performed by several technology-related websites, some of which are listed at the bottom of this article.

LCD, plasma, and DLP displays, unlike CRTs, have a native resolution. That is, they have a fixed grid of pixels on the screen that show the image sharpest when running at the native resolution (so nothing has to be scaled full-size which blurs the image). In order to display non-native resolutions, such displays must use video scalers, which are built into most modern monitors. As an example, a display that has a native resolution of 1600x1200 being provided a signal of 640x480 must scale width and height by 2.5x to display the image provided by the computer on the native pixels. In order to do this, while producing as few artifacts as possible, advanced signal processing is required, which can be a source of introduced latency. Interlaced video signals such as 480i and 1080i require a deinterlacing step that adds lag. Anecdotallyprogressive scanning mode. External devices have also been shown to reduce overall latency by providing faster image-space resizing algorithms than those present in the LCD screen.

Many LCDs also use a technology called "overdrive" which buffers several frames ahead and processes the image to reduce blurring and streaks left by ghosting. The effect is that everything is displayed on the screen several frames after it was transmitted by the video source.

Display lag can be measured using a test device such as the Video Signal Input Lag Tester. Despite its name, the device cannot independently measure input lag. It can only measure input lag and response time together.

Lacking a measurement device, measurement can be performed using a test display (the display being measured), a control display (usually a CRT) that would ideally have negligible display lag, a computer capable of mirroring an output to the two displays, stopwatch software, and a high-speed camera pointed at the two displays running the stopwatch program. The lag time is measured by taking a photograph of the displays running the stopwatch software, then subtracting the two times on the displays in the photograph. This method only measures the difference in display lag between two displays and cannot determine the absolute display lag of a single display. CRTs are preferable to use as a control display because their display lag is typically negligible. However, video mirroring does not guarantee that the same image will be sent to each display at the same point in time.

In the past it was seen as common knowledge that the results of this test were exact as they seemed to be easily reproducible, even when the displays were plugged into different ports and different cards, which suggested that the effect is attributable to the display and not the computer system. An in depth analysis that has been released on the German website Prad.de revealed that these assumptions have been wrong. Averaging measurements as described above lead to comparable results because they include the same amount of systematic errors. As seen on different monitor reviews the so determined values for the display lag for the very same monitor model differ by margins up to 16 ms or even more.

To minimize the effects of asynchronous display outputs (the points of time an image is transferred to each monitor is different or the actual used frequency for each monitor is different) a highly specialized software application called SMTT

Several approaches to measure display lag have been restarted in slightly changed ways but still reintroduced old problems, that have already been solved by the former mentioned SMTT. One such method involves connecting a laptop to an HDTV through a composite connection and run a timecode that shows on the laptop"s screen and the HDTV simultaneously and recording both screens with a separate video recorder. When the video of both screens is paused, the difference in time shown on both displays have been interpreted as an estimation for the display lag.16 ms or even more.

Display lag contributes to the overall latency in the interface chain of the user"s inputs (mouse, keyboard, etc.) to the graphics card to the monitor. Depending on the monitor, display lag times between 10-68 ms have been measured. However, the effects of the delay on the user depend on each user"s own sensitivity to it.

Display lag is most noticeable in games (especially older video-game consoles), with different games affecting the perception of delay. For instance, in PvE, a slight input delay is not as critical compared to PvP, or to other games favoring quick reflexes like

If the game"s controller produces additional feedback (rumble, the Wii Remote"s speaker, etc.), then the display lag will cause this feedback to not accurately match up with the visuals on-screen, possibly causing extra disorientation (e.g. feeling the controller rumble a split second before a crash into a wall).

TV viewers can be affected as well. If a home theater receiver with external speakers is used, then the display lag causes the audio to be heard earlier than the picture is seen. "Early" audio is more jarring than "late" audio. Many home-theater receivers have a manual audio-delay adjustment which can be set to compensate for display latency.

Many televisions, scalers and other consumer-display devices now offer what is often called a "game mode" in which the extensive preprocessing responsible for additional lag is specifically sacrificed to decrease, but not eliminate, latency. While typically intended for videogame consoles, this feature is also useful for other interactive applications. Similar options have long been available on home audio hardware and modems for the same reason. Connection through VGA cable or component should eliminate perceivable input lag on many TVs even if they already have a game mode. Advanced post-processing is non existent on analog connection and the signal traverses without delay.

A television may have a picture mode that reduces display lag for computers. Some Samsung and LG televisions automatically reduce lag for a specific input port if the user renames the port to "PC".

LCD screens with a high response-time value often do not give satisfactory experience when viewing fast-moving images (they often leave streaks or blur; called ghosting). But an LCD screen with both high response time and significant display lag is unsuitable for playing fast-paced computer games or performing fast high-accuracy operations on the screen, due to the mouse cursor lagging behind.

origin of lag in lcd displays manufacturer

One of the areas where the A-MVA panel does extremely well is in the areas of display lag and pixel response time. Just to recap, you may have heard complaints about "input lag" on various LCDs, so that"s one area we look at in our LCD reviews. We put input lag in quotation marks because while many people call it "input lag", the reality is that this lag occurs somewhere within the LCD panel circuitry, or perhaps even at the level of the liquid crystals. Where this lag occurs isn"t the concern; instead, we just want to measure the duration of the lag. That"s why we prefer to call it "processing lag" or "display lag".

To test for display lag, we run the Wings of Fury benchmark in 3DMark03, with the output set to the native LCD resolution - in this case 1920x1200. Our test system is a quad-core Q6600 running a Radeon HD 3870 on a Gigabyte GA-X38-DQ6 motherboard - we had to disable CrossFire support in order to output the content to both displays. We connect the test LCD and a reference LCD to two outputs from the Radeon 3870 and set the monitors to run in clone mode.

The reference Monitor is an HP LP3065, which we have found to be one of the best LCDs we currently possess in terms of not having display lag. (The lack of a built-in scaler probably has something to do with this.) While we know some of you would like us to compare performance to a CRT, that"s not something we have around our offices anymore. Instead, we are looking at relative performance, and it"s possible that the HP LP3065 has 20ms of lag compared to a good CRT - or maybe not. Either way, the relative lag is constant, so even if a CRT is faster at updating, we can at least see if an LCD is equal to or better than our reference display.

While the benchmark is looping, we snap a bunch of pictures of the two LCDs sitting side-by-side (using a relatively fast shutter speed). 3DMark03 shows the runtime with a resolution of 10ms at the bottom of the display, and we can use this to estimate whether a particular LCD has more or less processing lag than our reference LCD. We sort through the images and discard any where the times shown on the LCDs are not clearly legible, until we are left with 10 images for each test LCD. We record the difference in time relative to the HP LP3065 and average the 10 results to come up with an estimated processing lag value, with lower numbers being better. Negative numbers indicate a display is faster than the HP LP3065, while positive numbers mean the HP is faster and has less lag.

It"s important to note that this is merely an estimate - whatever the reference monitor happens to be, there are some inherent limitations. For one, LCDs only refresh their display 60 times per second, so we cannot specifically measure anything less than approximately 17ms with 100% accuracy. Second, the two LCDs can have mismatched vertical synchronizations, so it"s entirely possible to end up with a one frame difference on the time readout because of this. That"s why we average the results of 10 images, and we are confident that our test procedure can at least show when there is a consistent lag/internal processing delay. Here is a summary of our results for the displays we have tested so far.

As you can see, all of the S-PVA panels we have tested to date show a significant amount of input lag, ranging from 20ms up to 40ms. In contrast, the TN and S-IPS panels show little to no processing lag (relative to the HP LP3065). The BenQ FP241VW performs similarly to the TN and IPS panels, with an average display lag of 2ms - not something you would actually notice compared to other LCDs. Obviously, if you"re concerned with display lag at all, you"ll want to avoid S-PVA panels for the time being. That"s unfortunate, considering S-PVA panels perform very well in other areas.

Despite what the manufacturers might advertise as their average pixel response time, we found most of the LCDs are basically equal in this area - they all show roughly a one frame "lag", which equates to a response time of around 16ms. In our experience, processing lag is far more of a concern than pixel response times. Taking a closer look at just the FP241VW, we can see the typical one frame lag in terms of pixel response time. However, the panel does appear to be a little faster in response time than some of the other panels we"ve tested (notice how the "ghost image" isn"t as visible as on the HP LP3065), and we didn"t see parts of three frames in any of the test images.

After the initial article went live, one of our readers who works in the display industry sent me an email. He provides some interesting information about the causes of image lag. Below is an (edited) excerpt from his email. (He wished to remain anonymous.)

PVA and MVA have inherent drawbacks with respect to LCD response time, especially gray-to-gray. To address this shortcoming, companies have invested in ASICs that perform a trick generically referred to as "overshoot." The liquid crystal (LC) material in *VA responds sluggishly to small voltage changes (a change from one gray level to another). To fix this, the ASIC does some image processing and basically applies an overvoltage to the electrodes of the affected pixel to spur the LC material into rapid movement. Eventually the correct settling voltage is applied to hold the pixel at the required level matching the input drive level.

It"s very complicated math taking place in the ASIC in real time. It works well but with an important caveat: it requires a frame buffer. What this means is that as video comes into the panel, there is a memory device that can capture one whole video frame and hold it. After comparing it to the next incoming frame, the required overshoot calculations are made. Only then is the first captured frame released to the panel"s timing controller, which is when the frame is rendered to the screen. As you may have already guessed, that causes at least one frame time worth of lag (17ms).

Some companies discovered some unintended artifacts in their overshoot calculations and the only way they saw to correct these was to allow for their algorithm to look ahead by two frames instead of one. So they had to up the memory of the frame buffer and now they started capturing and holding not one but two frames upon which they make their complex overshoot predictions to apply the corrected pixel drive levels and reduce gray-to-gray response time (at the expense of lag time). Again, it works very well for improving response time, but at the expense of causing lag, which gamers hate. That in a nutshell is the basis of around 33ms of the lag measured with S-PVA.

Not every display uses this approach, but this could account for the increase in display lag between earlier S-PVA and later S-PVA panels. It"s also important to note that I tested the Dell 2408WFP revision A00, and apparently revision A01 does not have as much lag. I have not been able to confirm this personally, however. The above also suggest that displays designed to provide a higher image quality through various signal processing techniques could end up with more display lag caused by the microchip and microcode, which makes sense. Now all we need are better algorithms and technologies in order to reduce the need for all of this extra image processing -- or as we have seen with some displays (particularly HDTVs), the ability to disable the image processing.

origin of lag in lcd displays manufacturer

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origin of lag in lcd displays manufacturer

Display lag is a phenomenon associated with some types of LCD displays, and nearly all types of HDTVs, that refers to latency, or lag measured by the difference between the time a signal is input into a display and the time it is shown by the display. This lag time has been measured as high as 68ms, or the equivalent of 3-4 frames on a 60 Hz display. Display lag is not to be confused with pixel response time.

For older analog cathode ray tube technology, display lag is extremely low due to the nature of the technology which does not have the ability to store image data before display. The picture signal is minimally processed internally, simply for demodulation from a radio frequency carrier wave (for televisions), and then splitting into separate signals for the red, green, and blue electron guns, and for timing of the vertical and horizontal sync. Image adjustments typically involved reshaping the signal waveform but without storage, so the image is written to the screen as fast as it is received, with only nanoseconds of delay for the signal to traverse the wiring inside the device from input to the screen.

For modern digital signals, significant computer processing power and memory storage is needed to prepare an input signal for display. For over-the-air or cable-TV, the same analog demodulation techniques are used, but after that the signal is converted to digital data which must be decompressed using the MPEG codec, and rendered into an image bitmap stored in a frame buffer. This frame buffer is then procedurally written to the display device. In its simplest form this processing may take several microseconds to occur.

While the pixel response time of the display is usually listed in the monitor"s specifications, no manufacturers advertise the display lag of their displays, likely because the trend has been to increase display lag as manufacturers find more ways to process input at the display level before it is shown. Possible culprits are the processing overhead of HDCP, DRM, and also DSP techniques employed to reduce the effects of ghosting - and the cause may vary depending on the model of display. Investigations have been performed by several technology related websites; some of which are listed at the bottom of this article.

LCD, plasma, and DLP displays, unlike CRTs, have a native resolution. That is, they have a fixed grid of pixels on the screen that show the image sharpest when running at the native resolution (so nothing has to be scaled full-size which blurs the image). In order to display non-native resolutions, such displays must use video scalers, which are built into most modern monitors. As an example, a display that has a native resolution of 1600x1200 being provided a signal of 640x480 must scale width and height by 2.5x to display the image provided by the computer on the native pixels. In order to do this while producing as few artifacts as possible, advanced signal processing is required, which can be a source of introduced latency. Interlaced video signals such as 480i and 1080i require a deinterlacing step that adds lag. Anecdotally, display lag is significantly less when displays operate in native resolutions for a given LCD screen and in a progressive scanning mode. External devices have also been shown to reduce overall latency by providing faster image-space resizing algorithms than those present in the LCD screen.

Many LCDs also use a technology called "overdrive" which buffers several frames ahead and processes the image to reduce blurring and streaks left by ghosting. The effect is that everything is displayed on the screen several frames after it was transmitted by the video source.[citation needed]

Showing the existence of input lag requires a test display (the display being measured), a control display (usually a CRT) that would ideally have no display lag, a computer capable of mirroring output to two displays, stopwatch software, and a high-speed camera pointed at the two displays running the stopwatch program. The lag time is measured by taking a photograph of the displays running the stopwatch software, then subtracting the two times on the displays in the photograph. This method only measures the difference in display lag between two displays and cannot determine the absolute display lag of a single display. CRTs are preferable to use as a control display because their display lag is typically negligible. Also, video mirroring does not guarantee that the same image will be sent to each display at the same point in time.

In the past it was seen as common knowledge that the results of this test were exact as they seemed to be easily reproducible, even when the displays were plugged into different ports and different cards, which suggested that the effect is attributable to the display and not the computer system. An in depth analysis that has been released on the German website Prad.de revealed that these assumptions have been wrong. Averaging measurements as described above lead to comparable results because they include the same amount of systematic errors. As seen on different monitor reviews the so determined values for the display lag for the very same monitor model differ by margins up to 16 ms or even more.

To minimize the effects of asynchronous display outputs (the points of time an image is transferred to each monitor is different or the actual used frequency for each monitor is different) a highly specialized software called SMTT or a very complex and expensive test environment has to be used.

Several approaches to measure display lag have been restarted in slightly changed ways but still reintroduced old problems, that have already been solved by the former mentioned SMTT. One such method involves connecting a laptop to an HDTV through a composite connection and run a timecode that shows on the laptop"s screen and the HDTV simultaneously and recording both screens with a separate video recorder. When the video of both screens is paused, the difference in time shown on both displays have been interpreted as an estimation for the display lag. Nevertheless this is almost identical to the use of casual stopwatches on two monitors using a "clone view" monitor setup as it does not care about the missing synchronisation between the composite video signal and the display of the laptop"s screen or the display lag of that screen or the detail that the vertical screen refresh of the two monitors is still asynchronous and not linked to each other. Even if v-sync is activated in the driver of the graphics card the video signals of the analog and the digital output will not be synchronized. Therefore it is impossible to use a single stop watch for display lag measurements, nervertheless if it is created by a timecode or a simple stopwatch application, as it will always cause an error of up to 16 ms or even more.

Display lag contributes to the overall latency in the interface chain of the user"s inputs (mouse, keyboard, etc.) to the graphics card to the monitor. Depending on the monitor, display lag times between 10ms and 68ms have been measured. However, the effects of the delay on the user depend on the user"s own sensitivity to it.

Display lag is most noticeable in games (especially older video game consoles), with different games affecting the perception of delay. For instance, in World of Warcraft"s PvE, a slight input delay isn"t as critical compared to PvP, or to games favoring quick reflexes like Counter-Strike. Rhythm based games such as Guitar Hero also require exact timing; display lag will create a noticeable offset between the music and the on-screen prompts. Notably, many games of this type include an option that attempts to calibrate for display lag. Arguably, fighting games such as Street Fighter and Tekken are the most affected, since they may require move inputs within extremely tight windows that sometimes only last 1-3 frames on screen.

If the game"s controller produces additional feedback (rumble, the Wii Remote"s speaker, etc.), then the display lag will cause this feedback to not accurately match up with the visuals on-screen, possibly causing extra disorientation (e.g. feeling the controller rumble a split second before a crash into a wall).

TV viewers can be affected as well. If a home theater receiver with external speakers is used then the display lag causes the audio to be heard earlier than the picture is seen. "Early" audio is more jarring than "late" audio. Many home theater receivers have a manual audio delay adjustment which can be set to compensate for display latency.

Many televisions, scalers and other consumer display devices now offer what is often called a "game mode," in which the extensive preprocessing responsible for additional lag is specifically sacrificed to decrease, but not eliminate, latency. While typically intended for videogame consoles, this feature is also useful for other interactive applications. Similar options have long been available on home audio hardware and modems for the same reason.

LCD screens with a high response time value often do not give satisfactory experience when viewing fast moving images (They often leave streaks or blur; called ghosting). But an LCD screen with both high response time and significant display lag is unsuitable for playing fast paced computer games or performing fast high accuracy operations on the screen due to the mouse cursor lagging behind. Manufacturers only state the response time of their displays and do not inform customers of the display lag value.

The process that occurs from when the user presses a button to when the screen reacts is outlined below (steps which have negligible response time contributions have been omitted). Each step in the process adds response time (commonly known as "input lag"), which varies from minor to noticeable.

1: Controller sends signal to console For wired controllers, this lag is negligible. For wireless controllers, opinions vary as to the effect of this lag. It is likely that opinions vary due to each user"s sensitivity to lag, model of wireless controller and the other equipment in the signal chain (i.e. the rest of their gaming setup).

2: Network lag (online gaming only) Since the console must know the current location of other players, there is sometimes a delay as this information travels over the network. This occurs in games where the input signals are "held" for several frames (to allow time for the data to arrive at every player"s console) before being used to render the next frame. At 25 FPS, holding 4 frames adds 40ms to the overall input lag.

3: Console processes information and sends frame output to television A console will send out a new frame once it has finished processing it. This is measured with the frame rate. Using Gran Turismo 5 as an example, the maximum theoretical framerate is 60 FPS (frames per second), which means the minimum theoretical input lag for the overall system is 17ms (note: the maximum real world FPS in 3D mode is 40-50 FPS). In situations where processor load is high (e.g. many cars are on-screen on a wet track), this can drop to 30 FPS (16 FPS for 3D mode) which is equivalent to 32ms.

4: Television processes frame (image correction, upscaling, etc.) and pixel changes colour This is the "input lag" of the television. Image processing (such as upscaling, 100 Hz, motion smoothing, edge smoothing) takes time and therefore adds some degree of input lag. It is generally considered that input lag of a television below 30ms is not noticeable, discussions on gaming forums tend to agree with this value. Once the frame has been processed, the final step is the pixel response time for the pixel to display the correct colour for the new frame.

Typical overall response times Overall response times (from controller input to display response) have been conducted in these tests: http://www.eurogamer.net/articles/digitalfoundry-lag-factor-article?page=2 It appears that overall input lag times of approximately 200ms are distracting to the gamer. It also appears that (excluding television input lag) 133ms is an average response time and the most sensitive games (first person shooters and Guitar Hero) achieve response times of 67ms (again, excluding television input lag).

origin of lag in lcd displays manufacturer

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origin of lag in lcd displays manufacturer

When you"re using a monitor, you want your actions to appear on the screen almost instantly, whether you"re typing, clicking through websites, or gaming. If you have high input lag, you"ll notice a delay from the time you type something on your keyboard or when you move your mouse to when it appears on the screen, and this can make the monitor almost unusable.

For gamers, low input lag is even more important because it can be the difference between winning and losing in games. A monitor"s input lag isn"t the only factor in the total amount of input lag because there"s also delay caused by your keyboard/mouse, PC, and internet connection. However, having a monitor with low input lag is one of the first steps in ensuring you get a responsive gaming experience.

Any monitor adds at least a few milliseconds of input lag, but most of the time, it"s small enough that you won"t notice it at all. There are some cases where the input lag increases so much to the point where it becomes noticeable, but that"s very rare and may not necessarily only be caused by the monitor. Your peripherals, like keyboards and mice, add more latency than the monitor, so if you notice any delay, it"s likely because of those and not your screen.

There"s no definitive amount of input lag when people will start noticing it because everyone is different. A good estimate of around 30 ms is when it starts to become noticeable, but even a delay of 20 ms can be problematic for reaction-based games. You can try this tool that adds lag to simulate the difference between high and low input lag. You can use it to estimate how much input lag bothers you, but keep in mind this tool is relative and adds lag to the latency you already have.

There are three main reasons why there"s input lag during computer use, and it isn"t just the monitor that has input lag. There"s the acquisition of the image, the processing, and finally actually displaying it.

The acquisition of the image has to do with the source and not with the monitor. The more time it takes for the monitor to receive the source image, the more input lag there"ll be. This has never really been an issue with PCs since previous analog signals were virtually instant, and current digital interfaces like DisplayPort and HDMI have next to no inherent latency. However, some devices like wireless mice or keyboards may add delay. Bluetooth connections especially add latency, so if you want the lowest latency possible in the video acquisition phase, you should use a wired mouse or keyboard or get something wireless with very low latency.

Once the image is in a format that the video"s processor understands, it will apply at least some processing to alter the image somehow. A few examples:

The time this step takes is affected by the speed of the video processor and the total amount of processing. Although you can"t control the processor speed, you can control how many operations it needs to do by enabling and disabling settings. Most picture settings won"t affect the input lag, and monitors rarely have any image processing, which is why the input lag on monitors tends to be lower than on TVs. One of these settings that could add delay is variable refresh rate, but most modern monitors are good enough that the lag doesn"t increase much.

Once the monitor has processed the image, it"s ready to be displayed on the screen. This is the step where the video processor sends the image to the screen. The screen can"t change its state instantly, and there"s a slight delay from when the image is done processing to when it appears on screen. Our input lag measurements consider when the image first appears on the screen and not the time it takes for the image to fully appear (which has to do with our Response Time measurements). Overall, the time it takes to display the image has a big impact on the total input lag.

origin of lag in lcd displays manufacturer

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origin of lag in lcd displays manufacturer

Responsible for performing installations and repairs (motors, starters, fuses, electrical power to machine etc.) for industrial equipment and machines in order to support the achievement of Nelson-Miller’s business goals and objectives:

• Perform highly diversified duties to install and maintain electrical apparatus on production machines and any other facility equipment (Screen Print, Punch Press, Steel Rule Die, Automated Machines, Turret, Laser Cutting Machines, etc.).

• Provide electrical emergency/unscheduled diagnostics, repairs of production equipment during production and performs scheduled electrical maintenance repairs of production equipment during machine service.

origin of lag in lcd displays manufacturer

This invention relates to a method for scanning illumination light across the display area of a liquid crystal display panel so as to (1) improve the ability of such a panel to display motion and (2) accommodate the lag which liquid crystal materials exhibit in changing state.

For liquid crystal panels, there is a known problem with displaying motion due to the active matrix pixel element "holding" the charge for the entire frame, and therefore not responding with an impulse like a CRT. See, for example, U.S. Patent No. 6,636,190, which was published on March 28, 2002 as U.S. Patent Application Publication No. US

2002/0036608, Furuhashi, et al., "High Quality TFT-LCD System for Moving Picture," SID 02 Digest, Paper 48.3, pp. 1284-1287, May 2002, and Fisekovic, et al, "Scanning Backlight Parameters for Achieving the Best Picture Quality in AM LCD," Eurodisplay 2002, Paper P-41, pp. 533-535, 2002. This is especially a problem with sports imagery, where, for example, a golf ball can appear blurred or even missing.

The present invention addresses the problem of displaying motion in projection displays employing liquid crystal panels (e.g., rear or front projection TVs or monitors) and provides a clearer picture whenever there is motion while, in its preferred embodiments, retaining brightness.

In broadest concept, the invention involves scanning the illumination of a projection display in coordination with the refreshing of the information being displayed.

More particularly, the illumination is compressed into a stripe and then the stripe is swept across the frame (top to bottom typically) in synchronism with the updating of the image on the LCD, i.e., in synchronism with the frame refresh.

Preferably, such scanning is done without loss of brightness by providing the compressed illumination with the appropriate illuminance. Consider, for example, illuminating a one-third stripe of the display and then sweeping that portion across the entire display surface. If this area has the same total brightness as the display would have had if illuminated over its entire area, brightness will be conserved. In particular, for a one-third stripe, the stripe preferably has three times the illuminance it would have had if the entire display had been illuminated. Corresponding illuminance levels for strips having different dimensions are similarly determined, e.g., a one-fourth stripe preferably has four times the illuminance it would have had if the entire display had been illuminated. Sweeping of such a high illuminance stripe over the display conserves brightness.

By illuminating areas of the display for defined time periods, each line of the display can have light during the optimum time period when the display reaches its maximum or minimum intensity, thus increasing the display fidelity. By adding periods of darkness and compressing the time particular pixels or rows of pixels produce output light, the perceived effects of liquid crystal lag are reduced or eliminated.

Some of the lag exhibited by liquid crystal displays is due to slow liquid crystal motion, but at least part of the lag is due to the sample-hold function of the pixel elements and part of the lag can be attributed to the human eye. By "pulsing" the light for any particular pixel, row, or group of rows the liquid crystal (LC) can be made to appear faster, and more like a CRT with a refreshed flying-spot, which has an impulse response instead of a held response.

A faster responding LC and/or an increased frame rate can further aid in removing or completely eliminating lag. But at least partial reduction can occur even with slow response display materials and the typical 60 Hz refresh rate. The invention thus provides a method and associated apparatus for illuminating a liquid crystal panel which has a display area and comprises a plurality of rows which are sequentially addressed during a frame refresh cycle, said frame refresh cycle having a period T and each of the plurality of rows having a predetermined refresh time within the frame refresh cycle with the period of time between successive refresh times for each row (the cycle refresh period of the row) being equal to T, said method comprising:

(b) compressing the illumination light into a stripe which has an area smaller than the display area, said stripe being parallel to the plurality of rows (e.g., an area such that the ratio R of the stripe area to the display area is less than or equal to one third);

(c) using a moving optical element (e.g., a moving cylindrical lens or a rotating prism) to cause the stripe of illumination light to scan over the display area in a direction perpendicular to the plurality of rows, said direction corresponding to the direction in which the plurality of rows are sequentially addressed during a frame refresh cycle; and

(d) synchronizing the scanning of the stripe of illumination light with the frame refresh cycle so that for each row of the display, the majority of the illumination light which impinges on the row as a result of the scan is in the last half (or, alternatively, the last third) of the cycle refresh period for the row.

It should be noted that the foregoing method for illuminating a display panel is different from scrolling color systems where synchronization is with changes in the color of the illumination, not with the refresh cycle of the display. Examples of the use of scrolling color in connection with single panel LCoS systems can be found in: Shimizu, J.

A., "Scrolling Color LCOS for HDTV Rear Projection," SID 01 Digest, Paper 40.1, pp. 1072-1075, 2001; Brennesholtz, M. S. "Color-Sequential LCoS Projector with a Rotating Drum," SID 02 Digest, Paper 51.4, pp. 1346-1349, 2002; Janssen, P. "A novel single light valve high brightness HD color projector," Eurodisplay 1993, Paper LCP-1, pp. 249-256, 1993; and U.S. Patent No. 5,548,347. hi this way, the problems associated with displaying motion and the problems associated with changing the state of a liquid crystal material are addressed. The problem of reduced brightness is also addressed when the light source/compression system combination produces a stripe whose brightness is approximately 1/R times the brightness which would be produced if the entire display were illuminated, where R, as defined above, is less than 1.0.

Another embodiment of the invention is method for illuminating a display panel which has a display area and comprises a plurality of rows which are sequentially addressed during a frame refresh cycle. The frame refresh cycle has a period T and each of the plurality of rows has a predetermined refresh time within the frame refresh cycle with the period of time between successive refresh times for each row being the cycle refresh period for the row and being equal to T. The method includes

(b) compressing the illumination light into a stripe which has an area smaller than the display area, said stripe being parallel to the plurality of rows;

(d) synchronizing the scanning of the stripe of illumination light with the frame refresh cycle so that for each row of the display, the majority of the illumination light which impinges on that row as a result of the scan is in the last half of the cycle refresh period for that row. Yet another embodiment of the invention is a display which includes a light source, a display panel, a movable optical element, and a processor. The display panel includes a display area and a plurality of rows. The movable optical element is capable of compressing light from the light source into a stripe of illumination light that has an area smaller than the display area. The processor is configured and arranged to sequentially address each of the plurality of rows of the display panel during a frame refresh cycle to display an image, where the frame refresh cycle has a period T and each of the plurality of rows has a predetermined refresh time within the frame refresh cycle with the period of time between successive refresh times for each row being the cycle refresh period for the row and being equal to T. The processor is also configured and arranged to move the optical element to scan the stripe of illumination light sequentially over each of the plurality of rows in a synchronized manner so that the majority of the illumination light impinges on each row during the last half of the cycle refresh period for that row. The processor optionally includes two or more subprocessors.

Additional features of the invention are set forth in the description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. It is to be understood that both the foregoing general description and the following more detailed description are merely exemplary of the invention and are intended to provide an overview or framework for understanding the nature and character of the invention.

Figure 1 is a schematic illustration of a prior art illumination system. Figures 2 and 3 are schematic illustrations of representative apparatus for practicing the illumination method of the invention, hi particular, Figure 2 illustrates the use of a moving cylindrical lens to achieve sweeping, while Figure 3 illustrates the use of a rotating prism for the same purpose.

Figure 4 is a schematic drawing illustrating illumination light impinging on a representative top row and a representative middle row of the display area of a pixelized panel. Figures 5 and 6 are schematic drawings illustrating the temporal relationship between the scanning of illumination light and the refresh cycle for a panel in accordance with the invention, hi particular, Figure 5 A (5D) shows the liquid crystal (LC) drive signal for a representative top (middle) row of the display, Figure 5B (5E) shows the LC optical response of said representative top (middle) row, and Figure 5C (5F) illustrates representative timing of the illumination of said top (middle) row in accordance with the invention. Figures 6A, 6B, and 6C repeat Figures 5A, 5B, and 5C, respectively, and Figure 6D shows intended brightness, Figure 6E shows actual average perceived brightness with the static illumination approach of the prior art, and Figure 6F shows actual average perceived brightness with the swept illumination technique of the invention.

The invention is illustrated in the attached figures, where: (a) Figure 1 shows the prior art static illumination approach; (b) Figure 2 illustrates the swept illumination approach wherein a stripe is created by, in this case, a cylindrical lens which is moved vertically causing the stripe to be "swept" across the display surface (see U.S. Patent No. 5,398,082 for a discussion of the use of moving optical systems, including refractive and reflective systems, to sweep illumination); (c) Figure 3 illustrates the use of a rotating prism to create the desired sweeping (see U.S. Patent No. 5,548,347 and the Shimizu, Brennesholtz, and Janssen

(d) Figures 4-6 illustrate how brightness and/or accuracy of the display can be enhanced by illuminating a pixel (or row or group of rows) in coordination with its having attained its full on or off values, i.e., by coordinating the illumination stripe with the refresh cycle.

(lamp), 13 refers to a pixelized panel, 15 refers to a moving optical element, 17 refers to illumination light, and arrows 19 illustrate movement of moving optical element 15. Although not shown in these figures, relay optics and a light homogenizer are used between light source 11 and panel 13. See, for example, Magarill, U.S. Patent No.

5,625,738. The figures also do not show the projection lens which is used to project the image formed on the panel onto a rear or front projection screen. Although only one panel is shown in the figures, multiple panels can be used if desired. As illustrated in these figures, the process of this invention comprises:

(b) using a moving optical element to cause the smaller area (e.g., stripe illumination) to scan or sweep over (e.g., down) the surface of the display device, and (c) synchronizing the sweep to the display updating/refreshing (typically a row-at-a-time), i.e., scanning the illumination in synch with the display refresh.

In particular, Figure 5 illustrates how illumination pulses can be synchronized with the driving (refreshing) of representative top and middle rows of a display, while Figure 6 shows how such synchronization improves the image provided to the viewer by the representative top row of Figure 5. Similar improvements apply to the representative middle row of Figure 5, as well as to all other rows (or groups of rows) of the display as a result of the synchronization of the illumination with the refresh cycle.

As illustrated in, for example, Figures 5A/5C and Figures 5D/5F, for each row, the majority of the illumination light which impinges on the row as a result of the scanning of the illumination light is in the last half (e.g., the last third) of the cycle refresh period T for the row. As illustrated in Figures 6D, 6E, and 6F, by this coordination of the scanning (sweeping) of the illumination light with the refresh cycle, the actual average perceived

Although specific embodiments of the invention have been described and illustrated, it is to be understood that a variety of modifications which do not depart from the scope and spirit of the invention will be evident to persons of ordinary skill in the art from the foregoing disclosure.

origin of lag in lcd displays manufacturer

Your monitor’s display settings may increase the delay between inputting commands and seeing the result on your display. Some display parameters are configurable, while others are built into the hardware and cannot be changed.

The first thing to look at is your monitor’s refresh rate. A higher refresh rate increases the number of individual frames that your monitor displays per second. Displaying more frames per second reduces the delay between inputting a command and seeing its result on the screen, shaving valuable milliseconds off input lag.

Next, look at how your PC and display are connected. Wireless displays introduce more latency than wired ones, especially at high resolution display settings. If you’re using a wireless display, try switching to a wired connection, if possible.

Not all wired connections provide the same response time benefits. Some displays (especially Smart TVs) add processing effects like visual noise reduction to AV input, which adds to latency. To avoid this, check to see if your TV features a “Game Mode” that minimizes input lag by bypassing video signal processing.

Keep in mind that every TV and monitor has a unique, hardware-defined input latency. This is the amount of time that it takes the display to receive, process, and show incoming data. It is built into the hardware of the screen itself and cannot be changed.

Manufacturers don’t generally advertise their products’ latency delays. Instead, they focus on “response time,” which measures how long it takes for individual pixels to change color. It’s easy to confuse these two, but response time doesn’t have a significant impact on input lag.

Many new, gaming-ready displays have an input latency of 10-15 milliseconds. There are third-party websites that conduct and list monitor input latency scores, so it’s possible to verify how much of your input lag is built in.

origin of lag in lcd displays manufacturer

Yes we all know that CRTs have the lowest input lag of any display ever made. The problem with this longstanding fact is that any non-CRT screen is shunned by smashers as if they might contract the bubonic plague instantly upon use.

There has been talk of LCD monitors being used at upcoming international events such as Evo. This talk, as expected, has elicited a negative reaction from many smashers. The primary goal of this article is to outline just how close these monitors can get to the response time of a CRT, what the effect of lag is on gameplay, and to dispel some myths people have about LCD monitors.

In order to determine if a particular monitor lags, people will often try the subjective strategy. That is, they ask a smasher to play on a monitor and comment on how it feels. This strategy usually results in comments such as:

Fantastic responses! We have determined nothing. One major problem here is that smashers tend to placebo hard as soon as something that isn’t 2 feet in depth is placed in front of them. The other major problem is that humans are actually really bad at determining small fraction of a second differences.

With that said, it makes sense to attempt an objective strategy. With some help from Mofo, I developed a method for objectively testing lag on any type of screen. One of the beautiful things about this method is that it actually uses melee itself as part of the test. This means that we can say for a fact that every single possible source of lag has been accounted for.

As players, the lag we are sensitive to is the time between when an input is pressed to the time when the game’s reaction to that input appears on screen. In simpler words, lag is when stuff happens later than it should.

The game itself, however, cannot physically react to inputs immediately when they are received. This is because the game operates in discrete frames. For example, a character’s move can only ever begin on a frame, it cannot begin at any point in between. That said, players can and do press buttons in the time between frames. This means that if the A button is pushed to jab, the game will only begin the jab startup in a variable amount of time between 0 ms and 16.66 ms (length of one frame) – it will not start the jab immediately upon receiving the input.

The way this reality interacts with button combinations is rather interesting. It means that even if, on two separate occasions, the same two buttons are pressed with precisely the same delay in between, the same result is not guaranteed.

They understand the margin of error and press inputs in consequence to this. In the above graphic this would mean adding some time between button presses to guarantee the timing is always met

The point to make here is that, even on a monitor that is lagless, lag still exists in some way. A fully lagless experience is impossible. One way or another, players are capable of dealing with some lag. Lag induced by a laggy screen, however, is an added constant on top of this variable lag – the effect of which will be explored later.

The original concept for determining the latency of a monitor was to somehow detect the time difference between when an input is pressed to when a particular frame shows up on screen. Unfortunately, this approach is iffy at best for the reasons described in the previous section. The result of such a test would be (true lag) + (time until next frame) where time until next frame is between 0 and 16.66 ms. Luckily, there is another signal that is separate from the video and yet is related to it time wise – sound.

Let’s consider Captain Falcon standing on FD about to falcon punch. When the b button is registered by the console, the console will send the video frame information consistent with displaying a falcon punch as well as the sound information containing the famous words “FALCON PUNCH!”. The sound and the video will always be sent out by the console at the same times respective to each other, irrespective of where the input landed in the subframe region.

When the video signal reaches the display, it is first processed, and then displayed. This processing time is effectively the lag of the monitor – it will cause the two signals, audio and video, to appear desynchronized. It is the amount of time of this desynchronization that will be measured to determine lag.

When a player pauses a match in melee, two events happen nearly simultaneously: a white decal surrounds the screen and a high pitched sound is played, both denoting the pause has happened. These are both very strong and easy to recognize signals.

The audio output of the console is hooked up to an Arduino. The arduino lights an LED upon the detection of an audio signal. This effectively turns an audible signal (sound) into a visible signal (light).

When this test is executed on a CRT, the gold standard for response time, a time difference is obtained from step 4. This time difference is the expected value required if another system is to be called truly lagless.

When this test is executed on a laggy monitor, the time difference will be greater than what was seen on the CRT. The audio output will be detected at the same time but the pause decal will show up at some time later. The lag of this TV can then be calculated by the formula:

There are a few sources of error in the testing method. In order to improve the accuracy of the results, the test was executed multiple times on each monitor and the results averaged. That said, there is likely still about plus or minus 1 ms of error for the LCD results.

CRTs have less error associated with their measurement because determining when the video signal has appeared is less subjective. On an LCD, as can be seen in the gif above, the decal shows up in an incomplete fashion before the signal is accepted. This is done to provide a more fair comparison to the CRT – on which the top part of the decal is instantly fully clear.

If you have ever been introduced to the website www.displaylag.com, you might wonder how it is possible for the results to be so low with the RL2455HM.

The RL2455HM monitor displays a frame from top to bottom. This method of showing a frame is identical to how a CRT displays a frame. Display lag database uses the average latency across three zones (top, center, and bottom). Using this metric, even a CRT would not have zero lag – it would have 8.3 ms of lag. This is because it takes a full 16.66 ms to display the entire frame from top to bottom. In this particular case and in many others, when comparing to a CRT it is more fair to subtract about 8 ms from the number reported by Display Lag.

Because CRTs actually take time to display a whole frame, it is technically possible for a flat screen monitor to appear faster than a CRT. Given a small initial delay such as the RL2455HM + LGP and a faster refresh rate, it may be possible for the center of a frame and certainly the bottom of a frame to appear on screen earlier than it otherwise would on a CRT.

It is important to make a distinction between events that are affected by monitor lag and events that are not. Events that are executed via muscle memory timing, pressing one button at the correct timing after another, such as a wavedash are very easy to execute even on very laggy monitors because they do not utilize much visual prompting.

Let’s consider a person who can successfully power shield a laser 95% of the time. Assuming that human reaction follows the gaussian pattern, a gaussian response that could meet this success rate has a mean at 1 frame before the laser hits and a variance of about 72.25 (ms). Introducing the lag of the monitor and assuming that the distribution is shifted over by an amount equal to the lag, the probability of a successful power shield only drops to 93.7%.

Now a 95% success rate on a power shield is rather good. Let’s assume the person is still good but not super human – they have a lower success rate of 50% caused by an increase in variance. Given the same amount of lag, their success rate only drops to 49.7%. The takeaway from this is that given a higher variance, larger variation in a person’s ability to respond in a given amount of time, the effect of monitor latency diminishes.

It is also possible for the mean to not be perfectly centered along the target area. For example, consider a person has the same variance as described in the first example – a variance which signifies the person is quite proficient at hitting a 2 frame window. Now consider that this person tends to power shield late, late enough that their success rate is only 62.3% on a lagless system. With the lag added, this person’s success rate would drop to 49.1%. This scenario is just about the worst case given this kind of variance. The best case scenario is when the lag actually helps the player. If the same person had a tendency to hit early instead, their success rate would actually increase from 62.3% to 74.2%.

Notice that in the example where the percent of success dropped from 62.3% to 49.1%, the person was not extremely proficient at hitting the window to begin with. In contrast, when the success rate was 95% to start, the percent of success dropped a very small amount. A person proficient at hitting a 1 or 2 frame window either has a mean that is very close to centered on that target window, or has a very small variance. That said, there is a limit to how small a human’s variance can be. If a person has a 95%+ success rate hitting a 1 or 2 frame window, it is likely safe to assume it is caused by a well placed mean. Hence, players that can hit these timings very often will be very minimally affected by the added latency.

Now let’s talk about if the lag was a bit worse. Let’s consider a monitor that is slow by one full frame, 16.66 ms. In the first example with the 95% success rate person, their rate on this monitor would drop all the way to 50%. That is, 93.7% on a 2.86 ms monitor, 50% on a 16.66 ms monitor. This highlights the fact that there is a major difference between a monitor that is pretty good and one that is very good. Most monitors that people have tried would likely fall under the “pretty good” category at best. Do not allow past experiences with other monitors to influence your conception of these “very good” monitors.

All the calculations in this section were made under the assumption that the human does not adapt to the new lag. It may also be possible that the brain notices the slight offset and corrects to some degree. If the brain does do some correction, then the difference would be even smaller than described.

By the reasoning outlined in the previous section, minor lag does not appear to be a major factor for player performance. That said, I ask the reader, have you ever heard someone claim that some CRTs lag? Why do people think this? In my test results, CRT 2 is a 14 inch CRT. I have heard many negative comments about CRT 2. People just don’t seem to like it, often claiming that it lags. As shown by the results, the lag difference is essentially non-existent – it is well within the error of the test. So then, why do people not like it?

My theory is that people are also sensitive to image distortion. CRT 2 has a very clear image, but being a small monitor, it has a rather rounded screen. This rounded screen causes the image to appear somewhat distorted. This is very minor and difficult to notice but it may be the cause for the hate it has received.

The takeaway here is that lag is not the only problem with a screen. When an image looks different than another, it can throw a player off. This precise issue leads to one of the most powerful arguments for having a pro-LCD position. All the screens are the same. No more swapping back and forth between small CRTs and large CRTs. No more old, ugly, discolored CRTs. No more terrible terrible audio. The same image – same experience – every time.

It is true that very fast monitors such as the RL2455HM have some problems. Periods of fast movement can lead to minor ghosting. But overall the image quality is extremely good. After a few hours of using one, I full