Accurately Calibrate ALL Video Display Technologies
Each of the many different video display technologies available today has its own unique mechanical characteristics and unique distribution of light energy across the visible light spectrum. The Sencore ColorPro color analyzers provide you with a professional edge, with an optimized solution for accurate color analyzing and calibration of each of these display technologies! This article reviews the different popular display technologies and shows you the optimum Sencore Color Analyzer solution for each of these display types.
There are three Sencore Color Analyzer sensors available; the ColorPro III, ColorPro IV, and ProjectorPro (PP5006). Table 1 lists popular video display technologies and shows the correct ColorPro sensor to use with each.
| Display Type |
Sencore Color Sensor |
| LCD Flat Panel | ColorPro IV |
| DLP Rear Project | ColorPro IV |
| LCOS Rear Project | ColorPro IV |
| Plasma Panel | ColorPro III |
| CRT Rear Project | ColorPro III |
| CRT Direct-View | ColorPro III |
| Front Projectors (ALL) | ProjectorPro PP5006 |
Table 1. Recommended ColorPro/ProjectorPro sensor for each video display technology.
The sensors are teamed with one of three Sencore measurement software engines running on a PC, to fit your specific measurement or calibration application. The software options include the CP5000 ColorPro Color Analyzer, ACP6500 Auto CalPro Video Calibration System, or DC14 accuGray Gamma Calibration System.
Figure 1. Three specialized sensors insure optimum color analyzing and calibration accuracy on all video display technologies.
Calibrate Liquid Crystal Display (LCD) Direct View Displays
LCD (Liquid Crystal Display) TVs use a florescent backlight to send light through liquid crystal molecules and a polarizing substrate. LCD TVs have individual liquid crystal elements with red, green and blue pixels. The liquid crystal elements of each pixel are arranged so that, in their normal state, the light coming through the passive filter is polarized, so the light passes through the screen.
Figure 2. Liquid crystal sub pixels pass varied levels of light through red, green and blue filters, controlled by varying levels of applied voltage.
When a voltage is applied across the liquid crystal elements, they twist the light up to ninety degrees, in proportion to the voltage, thereby blocking the light's path at the polarizing filter. The applied voltage controls the degree of twist and hence the intensity of the red, green and blue light coming through each pixel to form the colored image on the display.
The ColorPro IV sensor, with its light tube technology, provides an accurate measurement of the light coming directly off the LCD flat panel, while disregarding the light coming off the panel at other angles.
Figure 3. LCD Direct View displays are popular in television, computer, and medical display applications. The ColorPro IV sensor provides accurate color analyzing measurements.
Calibrate Digital Light Projection (DLP) Displays
DLP™ display technology is based on an optical semiconductor device called a Digital Micromirror Device (DMD). It was invented by Texas Instruments (TI) in 1987. The DMD chip is basically an extremely precise light switch that enables light to be modulated digitally from microscopic mirrors spaced less than 1 micron apart.
Figure 4. The DLP display technology combines a color wheel and DMD device.
The mirrors are capable of switching thousands of times per second, directing light towards, and away from, a dedicated pixel space. The duration of the on/off timing determines the level of gray seen in the pixel. Current DMD chips can produce up to 1024 shades of gray. By integrating this grayscale capability with a six section color wheel (2x RGB), the DLP system is able to produce over 16 million colors.
The DLP rear projection display is calibrated using the ColorPro IV sensor. It provides the proper sampling characteristics and accuracy.
Figure 5. DLP rear project displays are calibrated
using the ColorPro IV sensor.
Calibrate LCOS (Liquid Crystal On Silicon) Displays
Figure 6. A look at the
LCOS module,
the heart of the
LCOS display technologyLCOS (Liquid Crystal On Silicon) is a technology that combines semiconductor and liquid crystal technologies together. Other brand names for this technology include D-ILA, SXRD, and Liquid Fidelity. The LCOS module consists of a liquid crystal layer which sits on top of a pixelated, highly reflective substrate. Below the reflective substrate is a layer of electronics to activate the pixels.
This assembly is combined into a panel and packaged for use in a projection subsystem. The polarized light source is separated into Red, Green and Blue color. These three beams of light project onto the LCD and reflect back. The polarized lights go through the liquid crystal on top of the silicon, which change polarization direction accordingly. As a result, an image is created from the pixel matrix on the silicon.
The Sencore color analyzer makes easy work out of measuring and calibrating LCOS rear projection displays. Use the ColorPro IV sensor, as shown, for accurate test results.
Figure 7. LCOS (Liquid Crystal On Silicon) rear projector technology.
Use the ColorPro IV sensor as shown for accurate color calibration.
Calibrate Popular Plasma Display Panels
Figure 8. Plasma displays excite inert
gases that result in ultra-violet
energy exciting phosphors.Plasma display panels (PDPs) are essentially a matrix of very small fluorescent tubes each containing either red, green, or blue phosphors. As in ordinary fluorescent tubes, a discharge is initiated by a high voltage which excites a mixture of inert gases such as He and Xe to a plasma state.
Upon relaxation, ultra-violet (UV) radiation is generated, which excites the colored phosphors. Phosphors are chemical compounds on the back glass that emit the visible light that makes up the picture we see. Just like a CRT television, the plasma display varies the intensities of the different phosphors to produce a full range of colors.
The Sencore ColorPro III sensor is specifically designed to accurately measure phosphor-based displays.
Figure 9. Plasma display technology continues to grow in popularity.
Color calibration is provided with the ColorPro III sensor.
Calibrate CRT Direct-View Displays
Figure 10. A cathode ray tube (CRT)
contains 3 electron guns which create
electrons that travel to their
respective red, green or blue
phosphors on the CRT face.A cathode ray tube (CRT) contains three electron guns, which cause electrons to travel at high speed toward their respective red, green or blue phosphors on the CRT's front glass. The electrons strike the phosphors, producing red, green, or blue light. The electron intensity is varied, causing varied levels of light, producing a picture image as the beams are deflected top to bottom and side to side during an electromagnetic scanning process.
Again, the Sencore ColorPro III sensor is used to accurately measure the phosphor-produced light output.
Figure 11. Direct-view CRT displays use phosphor emission on the face of the CRT.
The ColorPro III sensor is used with phosphor produced light on CRT displays.
Calibrate CRT Rear Projection Displays
Rear projection CRT technology displays use three separate cathode ray tubes, typically seven inch CRTs, to develop three individual red, green and blue display images. The images are mirror-reflected to a front screen, where the individual pictures are precisely registered to each other (converged) to produce a colored image. Since the light is phosphor-based, the Sencore ColorPro III sensor is used for color calibration.
Figure 12. CRT rear project displays use three separate CRTs to register a color image to the screen. Phosphor-based technologies are accurately calibrated using the ColorPro III sensor.
Calibrate CRT Front Projector Displays
Figure 13. LCD projector technology illustrated. While there are several front projector technologies available, LCD projectors are a popular choice. Three Thin Film Transistor (TFT) devices are used for the light valves. Light from an ultrahigh pressure mercury (or other) lamp is split into red, green, and blue light using special dichroic mirrors or prisms, which each reflect a specific range of wavelengths and pass all other wavelengths of light.
After an image is created for each color by the LCDs, the three images are rejoined with a prism and projected. Light usability is better in a 3-Light Valve System than a 1-Light Valve System, as you can achieve greater color depth and contrast. This transmission method is utilized in both LCD front projection and rear projection systems.
The PP5006 ProjectorPro is the sensor of choice for measuring and calibrating front projectors. The unique boresight configuration of the ProjectorPro allows it to accurately measure a target area directly from the projection screen, while greatly minimizing the effects of ambient room light on the measurement. This gives you the convenience of being able to directly measure the combined projector/screen performance accurately, even in low to moderate ambient light conditions.
Figure 14. Front projector displays use various technologies to produce a projected image. No matter the light source technology, the ProjectorPro provides the best measurement accuracy while being most immune to ambient room light.
The Sencore ColorPro system provides solutions for calibrating all display types today and in the future. For additional information on the Sencore ColorPro solutions or related training on professional calibration theory and techniques, call 1-800 - SENCORE (736-2673) or visit the web at
http://www.sencore.com.
