grayscale lcd panel free sample

[Wenting Zhang] is clearly a fan of old school STN LCD displays, and was wondering how various older portable devices managed to drive monochrome LCDs panels with multiple grey levels. If the display controller supports multiple bits per pixel, it can use various techniques, such as PWM, in order to produce a pseudo-grayscale image. But, what if you have a monochrome-only display controller? With a sufficiently high pixel clock, can you use software on the application side of things to flip those pixels in such a manner as to give a reasonable looking grayscale image?

The thing is, our brains do weird things with the visual signals we perceive. Regions with the same gray value, will be pulsating at the same time, and the eye will be drawn to it and perceive flickering. So, the next trick was to try to decouple nearby pixels in such regions using a LFSR sequence, which did give an noticeable improvement. The real aim was to try to play video through the LCD, so after investigating spatial dithering, [Wenting] moved over to wondering if he could also dither in time, i.e. can the error in the time sequence be smoothed out in a similar manner, to make the video look better? By using a simple noise-shaper, the video looked noticeably smoother, and practically flicker free. Great results! All in all, this is a long video to watch, but so crammed with useful tricks that it is in our opinion definitely worthy of your time.

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This is a flexible e ink display, 1.54 inch, with 152x152 resolution, UC8151D, SPI interface, and the e ink panel supports partial refresh and 4 grayscale.

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A wide variety of monochrome tn lcd display options are available to you, You can also choose from original manufacturer, odm monochrome tn lcd display,As well as from tft, standard, and tn.

Consistent presentation of digital radiographic images at all locations within a medical center can help ensure a high level of patient care. Currently, liquid crystal displays (LCDs) are the electronic display technology of choice for viewing medical images. As the inherent luminance (and thereby perceived contrast) properties of different LCDs can vary substantially, calibration of the luminance response of these displays is required to ensure that observer perception of an image is consistent on all displays. The digital imaging and communication in medicine (DICOM) grayscale standard display function (GSDF) defines the luminance response of a display such that an observer’s perception of image contrast is consistent throughout the pixel value range of a displayed image. The main purpose of this work is to review the theoretical and practical aspects of calibration of LCDs to the GSDF. Included herein is a review of LCD technology, principles of calibration, and other practical aspects related to calibration and observer perception of images presented on LCDs. Both grayscale and color displays are considered, and the influence of ambient light on calibration and perception is discussed.

The purpose of this work is to provide an overview of DICOM grayscale calibration of medical imaging grade liquid crystal displays (LCDs). In the context of this work, a “medical imaging grade” display is a high-quality LCD, which is appropriate for medical image viewing. It has the general characteristics of minimal visual noise, an appropriately wide viewing angle range, minimal reflection of ambient light, and a grayscale luminance response that is calibrated to a known and accepted standard. Each of these display properties will be discussed, with greater detail and emphasis placed on grayscale calibration. Much of the information provided here has been presented previously by other authors and groups, and references to those works are provided. Successful calibration and use of LCDs in medical imaging requires an understanding of LCD technology. Therefore, a “Technology Overview” is provided. A combination of the GSDF and LCD technology provides the “Foundations of DICOM Calibration.” There are several “Practical Aspects of Calibration,” some of which will be discussed here. Grayscale calibration is evolving from inherently grayscale displays to grayscale calibration of color displays. The “Influence of Color” on the calibration of LCDs is underrepresented in the literature and will be discussed briefly. The light source of most LCDs is a combination of fluorescent lamps and light guides. Because the luminance output of the lamps changes over time, “Maintenance of Calibration” is required to ensure quality image presentation over time. Finally, there are several “Confounding Factors” to consider when calibrating and implementing medical imaging grade LCDs into clinical practice. These include the influence of viewing angle and ambient light. Whereas the influence of ambient light on the physical properties of a displayed image is well known, the influence of ambient light on the adaptation (and perception) of the human visual system is underrepresented in the medical imaging display literature and will be discussed briefly.

Whereas the theory of grayscale calibration of medical imaging grade LCDs is based on the known response of the human visual system to contrast stimuli, practical calibration is implemented to both accommodate and utilize the specifics of LCD technology. A basic understanding of LCD technology is essential to appreciate the methods and limitations of calibration.

An active matrix liquid crystal display is often described as an optical “stack” containing a light source, light diffusers, polarizers, color filters (especially in case of a color LCD), and thin-film transistor liquid crystal matrix. An example of an optical stack is shown in Figure 1. The backlight is a combination of a light source and optical light guides and diffusers that serve to create a uniform luminance across the LCD surface. The light source is commonly a cold-cathode fluorescent lamp and may be implemented truly as backlights or commonly as “side” lights that are positioned along the outer edge(s) of the display. Other light sources, such as light emitting diodes or xenon lamps may also be used. The amount of light transmitted through the panel is a function of the relative orientation of the rear and front polarizers and the influence of the liquid crystal on the polarized light. The liquid crystal is a thin fluid layer of elongated organic molecules between glass plates. Linear “etching” of the inner surfaces of the glass plates preferentially orients the molecules near these surfaces parallel to the direction of the etching. In a resting state, the orientation of the molecules is determined by the direction of the etched grooves. As voltage is applied across the crystal, the molecules tend to preferentially align their direction in relation to the electric field. Orthogonal direction etching of the top and bottom surfaces of the liquid crystal layer provides an inherent “twist” in the orientation of the elongated molecules when a voltage is applied across the crystal. As the polarized light interacts with the twisted crystal, the plane of polarization tends to twist with the crystal. If the front and rear polarizers are oriented perpendicular to one another and the preferential plane of the polarized light is unaffected by the crystal, then very little light will be transmitted through the panel. If the molecules are highly aligned to the orthogonally oriented etching (caused by an applied voltage), then the polarized light is twisted 90° to align with the orientation of the front polarizer and a large fraction of light is transmitted. The applied voltage level influences to what extent the elongated molecules twist, thereby influencing the orientation of the plane of propagation of the once polarized light, which ultimately determines the amount of light that is transmitted by a small portion of the liquid crystal display. This description of LCD construction and operation is provided an as example. Details of the design and function of a specific LCD may well vary from the example provided there. However, the basic interactions between light, the polarizers, and the liquid crystal are common for all LCDs.

Each addressable LCD pixel has three subpixel elements, regardless of whether the display is inherently a color or a grayscale LCD. The three subelements correspond to the standard red, green, and blue color channels (RGB). In a color LCD, the colors are created by the addition of RGB filters. The color filters are omitted in inherently grayscale LCDs. Example color and grayscale pixel elements are shown in Figure 2. The “chevron” shape on the left in Figure 2 and the linear subpixels shown on the right are typical of many types of displays. As will be discussed later, the three subpixels will prove to be useful for grayscale calibration.

Grayscale calibration of LCDs is especially important because there is generally poor consistency in the inherent response of these displays. For example, the luminance (and perceived) contrast of an uncalibrated LCD can vary greatly throughout the input digital driving level (DDL) range of a single display.

The intensity of light emitted by a display, or luminance, is typically specified to have units of candela per square meter (cd/m2). The relationship between cd/m2 and the older luminance unit foot-lamberts (fL) is given by 1 cd/m2 = 0.292 fL. Because LCDs are non-Lambertian surfaces, luminance is typically measured with a photometer, which has a narrow light acceptance angle (≤5°). Some photometers have a display to provide luminance measurements to the operator. Others interface with a computer, which can provide electronic data capture and display the luminance values. Often, medical imaging grade LCDs utilize a calibration software package that supports a limited number of photometers. For calibrating medical imaging grade displays, a photometer should be accurate to within 5% except for very low luminance levels (0.5 cd/m2) where an accuracy of 10% may suffice. The accuracy of any photometer used for calibrating medical imaging grade displays should be specified by the manufacturer. Note that photometers used for calibrating color LCDs have independent RGB measurement channels. This provides for calibration of the color tone as well as the luminance of color displays.

The goal of grayscale calibration of electronic displays is to ensure that images presented to an observer have equal perceived contrast appearance on all displays, independent of the luminance range of the display. To achieve this goal requires that, given a specific luminance scene, the contrast perceived by the human visual system (HVS) is well known. There are several experimental models of the perceived contrast of the human visual system. There are also multiple grayscale display function models, which have been and continue to be used to calibrate displays. These include the CIELAB display function (Commission Internationale de l’Eclariage), the log-luminance linear function,

Experience has shown that the overall perceived contrast of an image presented on two GSDF calibrated LCDs of similar contrast ratio but different luminance ranges exhibit similar (although not exactly the same) overall contrast appearance. Another recognized limitation of the Barten model (and thereby the GSDF) is that, for a particular uniform background luminance, the luminance change required to perceive the visual targets was determined with the HVS adapted to that background luminance. In radiographic image viewing the HVS adapts to an overall scene luminance, but is required to perceive anatomical detail over the relatively wide luminance range of a displayed image. Because the HVS perception is optimized for a relatively narrow luminance range near the adaptation luminance, perception of detail in the light and dark portions of an image may be somewhat compromised.

The DICOM grayscale standard display function describes a relationship between luminance and monitor input values such that the slope of the curve at any point, ie the contrast, is proportional (but not necessarily equal) to the contrast associated with a JND from the Barten model. The DICOM grayscale display function is often plotted graphically as luminance versus JND index (j), where the JND index values range from 0 to 1023. The DICOM grayscale display function is presented in Figure 3 this way. For a given luminance, the luminance change required to perceive a difference corresponds to a single JND. The model data have been fit to a polynomial, which provides a convenient mathematical transform to convert back and forth from units of luminance (cd/m2) to JNDj. The transform to convert from luminance (L) to JNDjj) is provided in Eq. j to luminance,,j transforms are available in tabular format.

To perform a DICOM calibration of a display, the desired postcalibration minimum (Lmin) and maximum (Lmax) luminance values are first identified. Because the luminance output of the backlights decreases over time, it may be reasonable to expect that the calibrated maximum luminance intensity selected may adversely affect the life expectancy of a display. The desired Lmax may be less than the maximum luminance that the device is capable of producing, Ldmax. Diagnostic monochrome monitors are now commonly calibrated for an Lmax of 400 to 600 cd/cm2, whereas color monitors used for clinical review will have an Lmax from 250 to 450 cd/cm2. Similarly, Lmin, corrected for ambient light effects, is often set to be larger than the black level of the display, Ldmin. The minimum possible Ldmin value is determined by the ability of an LCD to block the backlight.

Typical contrast ratios are in the range of 250 to 400 for color displays and up to 600 (or more) for inherently grayscale displays. Commonly, Lmin is specified to be slightly higher than the minimum possible value. This allows similar displays with different maximum luminance levels to be calibrated such that the luminance ratio Lmax/Lmin is the same and images appear with similar contrast.

After the Lmin and Lmax values have been specified, the corresponding JND index values (JNDmin and JNDmax) are determined using Eq. max and JNDmin defines the total number of JNDs (JNDtot) that the calibrated display can produce. For example, a display with Lmin = 0.5 cd/m2 and Lmax = 200 cd/m2 has corresponding JNDmin = 46.6 and JNDmax = 572.2. In this example, JNDtot = 525.6. Most computers, video display driver cards, and displays are capable of 8-bit graphics. Regardless of whether the display is color or grayscale, an 8-bit grayscale palette is typical. Therefore, there are typically N = 256 grayscale digital driving levels available to a display system. The purpose of calibration is to set the luminance output for each input DDL such that throughout the entire DDL range, a change in DDL results in a JND index change that is constant. To accomplish this, the total number of JNDs is divided by the number of DDLs, minus one. This defines the average number of JNDs per DDL (JNDave) of the calibrated display. Continuing with the example started above, JNDave = 525.6 / 255 = 2.06. The JNDDDL of each DDL is next calculated as

Luminance as a function of digital driving level (DDL) for an uncalibrated display and a display that is calibrated to the DICOM Grayscale Standard Display Function.

Just noticeable difference index value as a function of digital driving level (DDL) for an uncalibrated display and a display that is calibrated to the DICOM Grayscale Standard Display Function.

It is worth noting that calibrating displays to the GSDF with a similar luminance ratio can provide a similar image appearance on all displays, but this does not guarantee that the images necessarily look as desired. The overall appearance of digital medical images is dependent upon many variables including image acquisition parameters (peak kilovoltage [kVp] and mAs in x-ray, for example), image processing, and the various linear and nonlinear grayscale transforms provided for by DICOM Part 14.

As shown in Figures 4 and ​and5,5, a luminance output that corresponds to the GSDF is not inherent to LCDs. Calibration requires creation of a look-up table (LUT) such that for each DDL, the LUT specifies a new DDL value that corresponds to a displayed luminance that matches (as closely as possible) that of an ideal DICOM display.6 shows the JND/DDL contrast of an ideal GSDF calibrated display and a display that has been calibrated using an 8-bit LUT.

With the 8-bit-to-8-bit calibration, the net result is that the overall contrast of the display has the visual appearance of being calibrated. The overall perceptual contrast of the display is as desired. However, adjacent input pixel values may have output DDLs that are exactly the same, resulting in no displayed contrast between adjacent input levels. This effect is represented by the JND/DDL values in Figure 6, which have a value of zero. Also, adjacent input values may have output DDLs that differ by more than 1 (of 256) and the displayed contrast between adjacent input levels is excessive. This is also shown in Figure 6. Note that, for this example, the 8-bit-to-8-bit conversion resulted in 218 of a possible 256 unique gray levels in the calibrated grayscale function. The grayscale discontinuity caused by the 8-bit-to-8-bit LUT may result in “scalloping” or grayscale “banding” artifacts in a displayed image. Given that 8-bit-to-8-bit calibration generally results in loss of local contrast combined with excessive local contrast, it is generally not a satisfactory calibration method.

Use of an expanded grayscale palette, achieved by addressing the subpixels independently, provides the foundation for a more effective grayscale calibration. With the expanded palette, the output luminance can be made to more closely match the ideal luminance indicated by the GSDF. In contrast to the 8-bit palette, the same luminance value need not be used multiple times and the potential for very large and small contrast changes for adjacent DDLs is reduced. This results in a calibrated display, which more closely approximates that of an ideal display, as shown in Figure 6. Along with spatial dithering, the use of temporal modulation or temporal dithering of subpixels has been implemented by some manufacturers to further refine the luminance difference between LUT palette entries.

“Theory of Calibration” describes how a calibration LUT is derived once the desired Lmin and Lmax have been specified. For grayscale displays, typical calibrated Lmax values are in the range of 400 to 600 cd/m2. These displays generally have a contrast ratio of approximately 600:1. Therefore, Lmin could be specified as low as 0.66 to 1 cd/m2 to achieve a displayed luminance ratio equal to the device contrast ratio. Whereas the HVS can adapt to a large range of luminance levels, the luminance range of an adapted HVS is relatively limited.,Lmax = 525 and Lmin = 1.5 will have a luminance ratio of 350. The Lmax of color displays is generally less than that of grayscale displays, and may range between 250 and 450 cd/m2. For the same luminance ratio, a color monitor thus has a lower Lmin, making them more susceptible to the adverse effects of ambient light.

It is important to note that GSDF calibration of different displays does not necessarily result in displays which are exactly perceptually matched. The GSDF ensures that the perceived contrast is consistent throughout the grayscale range of a given display, but calibrated displays that have substantially different maximum luminance values or contrast ratios will not provide an exact perceptual match. For example, a brighter display will still look brighter after calibration and a higher contrast display will still have higher contrast. Because the luminance and contrast properties of medical imaging grade LCDs is not widely variable, GSDF calibration of these displays will ensure that an image presented on each display will have a similar appearance.

It might be considered that calibration based on initial measurement of the luminance at every palette LUT value provides the best grayscale calibration. For cathode ray tube (CRT) displays, luminance output is well behaved with driving level and most calibration software coarsely sampled the palette and interpolated the intervening values. Therefore, the typical number of luminance measurement points used for CRT calibration is often in the range of 18 to 32. Note that American Association of Physicists in Medicine (AAPM) TG18 recommends measurement of 18 points along the grayscale range to assess GSDF conformance. Therefore, a display that was calibrated using measurements from the same 18 points would be expected to have a favorable TG18 luminance response evaluation.

For LCD displays, the luminance can vary discontinuously between adjacent palette LUT entries. Therefore, the number of calibration points should be much larger than the number of points used for CRT devices, and preferably equal to the full size of the grayscale palette. Similarly, calibration conformance should be checked for all 256 drive levels.

Postcalibration measurement of the grayscale response of a display can be used to assess the quality of the calibration. Detailed discussion of the methods used to assess calibrated display performance are available in the literature.,,Lmin and Lmax. A comprehensive assessment of display grayscale calibration involves measuring the luminance for each of the 256 DDL values. For a small sample of displays, this may be done using a quality photometer and manual recording of the data. Preferably, this can be done by using a photometer that interfaces directly to a computer. Characterization of calibrated displays via measurement of all 256 steps in the DDL range provides an overall assessment of the grayscale response. Both “macro-grayscale” (over a subset of DDLs) and “micro-grayscale” (between individual DDLs) can be assessed. Macroscale assessment may be performed by calculating the JND/DDL contrast between DDL values that are coarsely spaced. For example, the large scale conformance to the GSDF may be calculated using DDL values that are separated by 15. This is equivalent to the 18-step assessment recommended by the AAPM TG-18. Of course, assessment of the macro-grayscale conformance does not require measurement at all 256 DDL values. The additional value of measuring the luminance at each of the 256 DDL values is characterization of the micro-grayscale response. This is more important for LCD displays than for CRT displays. Discrepancy between the ideal GSDF and the actual micro-grayscale response can be considered an assessment of the contribution of an imperfect grayscale calibration to the noise of the displayed image.

Figure 7 shows the macro- and micro-grayscale response of a calibrated grayscale display. The macro-grayscale JND/DDL contrast measurement may be considered to be a local average of the micro-grayscale measurement. As shown in Figure 7, the macro-grayscale measurements do not provide a good indication of the precision of the micro-grayscale response. The TG-18 report and the DICOM GDFS recommend calculating the root mean squared error (RMSE) of the micro-grayscale JND/DDL contrast to characterize the calibration precision. It may be reasonable to calculate the normalized RMSE (nRMSE) by dividing by the average JND/DDL. The nRMSE provides a measurement of the relative noise, which may be useful for comparing displays with different average JND/DDL contrast values. The average JND/DDL contrast of the micro-grayscale JND/DDL contrast of Figure 7 was 2.7; the RMSE was 0.29; and the nRMSE was 0.11. Note that calibration noise should be considered in a relative comparison to other sources of noise in the medical image acquisition and display chain.,

There are many possible mechanisms to store and utilize calibration data. Only an introduction to these mechanisms is provided here. Depending upon implementation, the calibration look-up table may be stored on a host PC as an International Color Consortium (.icc) color profile (or similar). The computer operating system, in combination with the video card, can modify the DDL values sent to the display via the .icc profile. As a general rule, the .icc profile is available to both analog or digital visual interface (DVI) video output formats. The calibration data may also be stored in firmware of the LCD. In general, this type of implementation has the limitation that it can be applied only to a DVI input signal, but has the advantage that the calibration is immediately available if the display is moved to another PC with a DVI output channel. Certainly, other vendor-specific solutions to calibration storage and portability exist. Also, note that many imaging grade displays have other calibrated display function settings in addition to the GSDF setting (such as log-linear or CIELab), which are provided by the manufacturer and delivered as part of a new display.

Not surprisingly, grayscale calibration was originally performed on inherently grayscale displays. Grayscale calibration of color LCDs for medical image display is a relatively new practice. The implications of color on the grayscale calibration palette were discussed in “Expanded Palette Calibration”. Color displays have an inherent advantage for displaying radiographic images that contain color, such as nuclear medicine, Doppler ultrasound, and functional magnetic resonance images. Also, recent work has indicated that using color displays likely does not limit the ability of an expert observer to diagnose disease in chest radiographs.

The construction of grayscale and color LCDs is similar, except that the color displays have red, green, and blue (RGB) color filters. Each of the color filters preferentially blocks a portion of the color spectrum contained in the “white” backlight source. Therefore, the maximum luminance output of color displays is considerably less than that of inherently grayscale displays. Although color displays are inherently dimmer than their grayscale counterparts, it is worth noting that there is currently an upward trend in the maximum luminance of color medical imaging grade LCDs.

All LCDs, including grayscale, have a color tone. The color tone of grayscale displays is a function of the fluorescent (or other) backlight and the transmission properties of the optical stack that may be included to adjust the color tone. For example, some grayscale displays have a blue hue similar to that of blue-base film. Contrary to what one might expect, identical models of grayscale displays may have noticeably different color tones. This is due primarily to variations in the manufacture of the backlights. The AAPM TG-18 report provides guidelines for establishing measurable color differences such that the color tone differences are not perceivable. The color tone of color displays can generally be specified during calibration. Therefore, it is reasonable to expect that no color difference should be perceived between similarly calibrated color displays.

Liquid crystal displays commonly use fluorescent lamps as the backlight source. The luminance output of the backlight is subject to change over time and therefore requires some sort of maintenance to ensure luminance stability. Most medical imaging grade displays have built-in backlight luminance sensors with feedback circuits to maintain the desired maximum luminance of the LCD based on proper calibration of the backlight sensor. Some of them also have sensors that measure the luminance output of a small area near the edge at the front of the display. The front of screen sensor has the potential to measure not only the maximum luminance, but can also be used to measure the luminance throughout the entire DDL range, albeit in a small area at the periphery of the display. The sensors in turn are calibrated with respect to the center of the LCD. That the front of screen sensor can measure luminance values throughout the entire DDL range can help to provide assurance that conformance to the GSDF is maintained over time. Whether an automated front of screen sensor is required to maintain conformance has not be established. Often, the sensor values are provided to administrative software that allows remote monitoring of the luminance properties as measured by back and/or front of screen sensors. Note that the luminance values obtained remotely are as reliable as the electronic sensors that measure them. Periodic, on-site evaluation of medical imaging grade LCDs is recommended to ensure overall display quality. Experience has shown that quarterly on-site evaluation is initially appropriate. It may be reasonable to modify the frequency of the on-site visits based on the frequency and severity of the problems found during these initial quarterly visits.

The luminance and contrast properties of LCDs are dependent upon the angle (with respect to the plane of the display face) from which the light photons are emitted and subsequently observed. Grayscale calibration of medical imaging grade LCDs assures conformance to the GSDF when a display is viewed from an angle perpendicular (or nearly so) to the display face. As has been recognized for some time, the changing optical properties of LCDs as a function of viewing angle can have a substantial influence on perceived contrast.,,,,8 shows an example of the change in the macro-grayscale conformance to the DICOM GSDF for various viewing angle deviations from perpendicular. In Figure 8, the data are plotted as the relative change in luminance contrast (dL/L) per DDL as a function of DDL. Notice that conformance to the standard starts to break down for relatively shallow viewing angle changes, where the viewing angle (θ) is the angular deviation from perpendicular and, for Figure 8, is specified along the horizontal axis of the display (φϕ = 0°). In Figure 9, note that the influence of viewing angle may vary for the long (ϕ = 90°) versus short axis (ϕ = 0°) of a display, or along diagonals (ϕ = 45°, 135°). The potential influence of viewing angle should be considered and accommodated during specification and installation, as well as routine use, of LCDs.

The light emitted by a LCD as luminance can be considered to carry useful image information. In general, ambient light, which is incident upon a display face (including front-of-screen shields and filters) and reflected back toward an observer, has the potential to degrade the contrast properties of the image or otherwise affect an observer’s perception of that image. Reflected ambient light is a source of luminance coming from the display face and acts in addition to the luminance generated by the display. The optical properties of a display dictate the influence of ambient light. “Specularly” reflected light represents a mirror-like reflection with only minimal spatial or angular spread.

As an example, consider an LCD with Lmin = 0.5 cd/m2 (JNDmin = 47), Lmax = 200 cd/m2 (JNDmax = 572), and a coefficient of diffuse reflection of 0.005 cd m−2 lx−15. A typical office might have an illuminance of 200 lx15. In this case, the reflected ambient light results in an additional luminance of 1 cd/m2, with corresponding Lmin = 0.5 + 1.0 cd/m2 (JNDmin = 90) and Lmax = 200 + 1 cd/m2 (JNDmax = 573). The ambient light resulted in a loss of 42 JNDs (of an original 525) to the overall display function. If the display was calibrated assuming zero contribution from ambient light, then the JND (and perceived contrast) loss occurs in the low DDL, low-luminance portion of the display function. The calibration software for most medical imaging grade displays can account for the loss of contrast as a result of ambient light. If a display is recalibrated to accommodate additional luminance from reflected ambient light, then the JND loss is distributed equally throughout the entire DDL range.

At first, it might seem that the best way to deal with ambient light is to eliminate it. However, it is reasonable to expect that LCDs will continue to be used in clinical environments that require illumination for patient care. Further, it has been found that a modest amount of radiology reading room illumination (25–40 lx) is preferable to no illumination.2. If the ambient light is set to a perceptually comfortable illuminance of 25 cd/m2, then the JND loss would be a modest 7 JNDs. An understanding of the influence of ambient light on the contrast properties of a displayed image and on the adaptation and comfort levels of the HVS should be used to manage (not necessarily eliminate) ambient light in clinical care settings.

“Assessing Calibration Quality” described how micro-grayscale measurements may be used to assess the contribution of display calibration to overall grayscale noise. The luminance measured with even a shallow angle photometer represents an average over many individual pixels. In this context, the micro-grayscale response was measured over a large (with respect to a single pixel) physical area. Smaller area variations in luminance result in spatial noise. That is, adjacent pixels addressed with the same DDL may have a different luminance output that contributes to an overall image noise. The spatial noise of LCDs has been described through precise measurement of the luminance of individual pixels,–,,,

Consistent presentation of digital radiographic images is essential for ensuring a high level of patient care. To help achieve consistent image presentation, the DICOM Standard includes a Standard Grayscale Display Function derived from the Barten model of the human visual system. The theoretical principles used to calibrate displays are well known and straightforward. The methods used for calibration of medical imaging grade liquid crystal displays specifically account for and utilize LCD technology. Precalibration considerations include specification of the calibrated luminance range. The manner in which ambient light influences the physical and perceived contrast of a display, and how it may be accommodated, should also be considered. Because LCDs are non-Lambertian light emitters, the luminance output and contrast properties of LCDs are dependent upon the angle from which they are viewed. Therefore, the accuracy of grayscale calibration is variable with viewing angle. Whereas the influence of viewing angle cannot be accommodated through calibration, it should be considered when evaluating and implementing LCDs in the clinical practice. Color LCD technology is improving and it seems likely that their use will become more common both within and outside radiology reading rooms. Grayscale calibration of color displays is conceptually similar to that of inherently gray displays and allows calibration of multiple displays to a common color tone. For both gray and color LCDs, measurement of the micro-grayscale is required to ensure both the accuracy and precision of the calibration. It is important to note that grayscale calibration alone is insufficient to ensure an overall high level of displayed image quality. Whereas not specifically considered here, other aspects of display quality, including resolution and spatial noise, also have to be considered to ensure a high-quality, medical imaging grade display

6. Digital Imaging and Communications in Medicine, Part 14: Grayscale Standard Display Function, published by National Electrical Manufacturer’s Association, 2001

9. Blume H, Ho AM, Stevens F, Steven PM. Practical aspects of grayscale calibration of display systems. PACS and Integrated Medical Information Systems: Design and Evaluation. SPIE.2001;4323:28–41. doi: 10.1117/12.435509. [CrossRef]

11. Flynn M, Tchou P. Accurate measurement of monochrome luminance palettes for the calibration of medical LCD monitors. Visualization, Image-Guided Procedures, and Display. SPIE.2003;5029:438–448. doi: 10.1117/12.480380. [CrossRef]

15. Langer S, Fetterly K, Mandrekar J, Harmsen S, Bartholmai B, Patton C, Bishop A, McCannel C. ROC Study of four LCD displays under typical medical center lighting conditions. J Digit Imaging.2006;19:30–40. doi: 10.1007/s10278-005-8149-y. PubMed] [CrossRef]

This study did not show any significant difference in image quality between a standard 2-MP color LCD display and a medical-grade 2-MP monochrome LCD display, neither using the contrast-detail phantom nor in the visual grading study. Our findings are in accordance with several studies that have shown similar performances for color and monochrome displays in a variety of clinical tasks such as brain CT,,2 was acceptable provided that the ambient illuminance was low.

The main purpose of calibrating a monitor according to DICOM part 14 is to obtain similar image presentation on all displays. A calibration distributes the total contrast of the display equally across the entire grayscale and objects will thus be presented with the same contrast regardless of whether they are present in bright or dark parts of the image. When the task is to find known objects in an image, such as targets in a contrast-detail phantom, the window/level controls can be used to optimize image contrast. The display’s contrast characteristics becomes less important and the noise properties become more important—noise from the image detector and noise from the image display. However, this does not mean that calibrating a display is meaningless. Clinical images have little resemblance to images of a contrast-detail phantom in that pathology might be present also in the bright or dark parts of the image. A consistent display of images is even more important when, for example, a current image is compared to a previous image on another display. Any differences between the images should be caused by the imaged object and not by the displays.

The main advantage of medical-grade monochrome displays is their high luminance, which makes it easier to see the entire grayscale from black to white in an image. In a recent report,

The tests with the contrast-detail phantom showed very small differences in image quality between the two types of displays. There was in fact a larger difference in image quality between the flat-panel detector and the storage phosphor plates (Fig. 2). It might thus be more appropriate to choose a better (more expensive) imaging system such as a flat-panel detector and use (cheaper) color displays than the opposite. Irrespective of the detector being used, there was a large interobserver variability, similar to what has been reported previously.2.

2.7 inch eink ePaper display with 264×176 resolution, SPI interface, supporting four grayscale display. Due to the bi-stable, the image once updated can stay on the display even when power is completely disconnected. The image is also high contrast and readable under sun just like printed paper. It is a perfect match for appliances like e-shelf label, smart tag, smart home application, industrial instrument and other related products.

Monochrome CRT displays are the most commonly used technology, especially in the medical industry. Due to its high-reliability performance at a low price, it has been highly adopted by medical, manufacturing, and gaming industry. With growing technical advancement in the electronics sector, there is a tremendous shift of CRT monitors to LCD monitors. LCD monochrome delivers more clarity, saves energy, has a high megapixel pictorial view, and provide high-quality images. This is expected to increase its market presence in the coming future and would offer high competition to CRT monochrome screen market. Whereas LED monochrome display, though would increase workspace optimization, is on the introduction stage of the market and has to beat the already acquired market of CRT and LCD monochrome displays thereby predicted to grow with steady growth during the forecast period of 2017 to 2023.

The monochrome display can be used for indoor and outdoor applications such as displaying monitored physical quantity (temperature, pressure, and vibration), displaying bold and large text, and for surveillance and traffic control. The monochrome display is used in various verticals, including consumer electronics, automotive, and manufacturing. Monochrome displays are extensively used in the medical sector for a wide area of applications including diagnostic display, surgical display, radiology display, clinical review displays. It has been adopted by hospitals, clinics, diagnostic centers, pathology labs, and others. In the consumer electronics industry, monochrome displays are used in television, graphics-based monitors, watches, smartphones, and wearable. Monochrome displays such as LCD and LEDs are used for wide automotive applications such as car navigation, instrument panel, and in rear seat monitors.

Display type segmentation of the monochrome display market comprises CRT, LCD, and LED display. The CRT segment accounted for the largest market share in 2017, while the LCD segment is expected to register the highest CAGR during the forecast period.

Monochrome display market, by region, has been segmented into Asia-Pacific, North America, Europe, and rest of the world. North America accounted for the largest market share of in 2017. Some of the factors that are responsible for the market growth include high adoption of advanced technology, a large market of display controllers, and high adoption of LCD and graphic monitor in various sectors. Asia-Pacific is expected to grow at the highest CAGR during the forecast period owing to factors such as an increase in healthcare expenditure, various healthcare initiatives by government, and the presence of leading Amber Monochrome Monitor manufacturers in China.

Modular 9.3" 4K Monochrome LCD for XiP, featuring a 52 micron pixel pitch. This module plugs directly into the XiP without the need to manually attach bus wires or seat the screen. Each LCD is rated at over 3,000 hours requiring 1-2 replacements per year based on printer usage.

But there"s one simple, effective method that you might not have ventured yet: Turning your phone"s display to grayscale. Removing all color from the screen can be a more effective deterrent than you might think.

It"s a simple trick, but one that works on our brains, which are attracted to anything bright and shiny. According to former Google design ethicist Tristan Harris, who has founded the Center for Humane Technology, going grayscale removes positive reinforcements and dampens that urge to to keep loading up social media feeds or mobile games.

If you"re using an iPhone as your daily handset of choice, open up the Settings app, then choose Accessibility > Display & Text Size > Color Filters. Turn the Color Filters toggle switch on, and Grayscale appears as the top option. Presto! All color has drained from your iPhone"s screen, until you toggle the switch off again.

If you"re on the stock or Pixel version of Android 9.0 or later, open up the Quick Settings panel with a two-finger swipe from the top of the screen, then tap the Pen icon on the lower left. Drag the Grayscale icon up into the panel of icons, and you"ll have one-tap access to your phone"s grayscale mode whenever you need it.

The grayscale toggle switch is part of a new Digital Wellbeing suite of tools built into the latest versions of Android. If you open up Settings, then tap Digital Wellbeing & parental control, then choose Wind Down, you can set up a schedule for the evening: Wind Down turns the screen gray, and mutes notifications.