Cromaclear
What is the CromaClear CRT?
A CROMACLEAR CRT is a CRT display technology, specifically optimized for rapidly emerging multimedia use. This CRT combines the best features of dot trio and aperture grille monitors into a unique slot mask. Utilizing a mask design already established in the television industry, which uses a similar slot design, CROMACLEAR CRTs excel in displaying video images.
The most significant difference between CROMACLEAR CRTs and existing CRT technologies is their viewable phosphor pattern. When combined with the slot mask, the red, green and blue (RGB) P22 phosphors of the CROMACLEAR CRT appear elliptical in shape, compared to round phosphors (used in dot-trio CRTs) and stripes (used in aperture-grille CRTs). The illuminated phosphors of the CROMACLEAR CRT are also grouped into separate bundles of three in a vertical alignment, providing improved clarity and focus.
With the CROMACLEAR CRT, the conventional “dot pitch” measurement is no longer applicable. The term “mask pitch” is more appropriate when discussing this specification. A mask pitch measurement is the distance between like-colored phosphors on the CROMACLEAR CRT mask. The mask pitch of the CROMACLEAR CRT is 0.25 mm dpi.
Image Quality and the CromaClear CRT
Overall monitor image quality is difficult to quantify. Given the inherent complex nature of CRTs, a variety of factors combine to produce a monitor image. These factors focus, contrast and color saturation all come into play when deciding which monitor and CRT provide the “best” image. When discussed in relation to the CROMACLEAR CRT, these items need further explanation.
Focus: The CROMACLEAR CRT incorporates a new SDF-ELA (Single Dynamic Focus – Expanded Large Aperture) gun for 15-inch tubes and DQF- ELA (Dynamic Quadruple Focus – Expanded Large Aperture) gun for 17-inch tubes. These guns provide uniform image clarity and focus. When viewing images in monitors corners, other CRTs could distort image ratio and perspective. Using the CROMACLEAR CRT ELA gun, this problem is virtually eliminated. This also provides improvements for viewing six-point text and fine, single-pixel elements.
As mentioned earlier, the CROMACLEAR CRT incorporates a new mask shape and alignment. As a result, the electron beam used to pass through the slot mask had to be adapted to match. The ELA gun utilized in CROMACLEAR CRTs has an exact beam/mask match (an elliptical electron beam passes through an elliptical mask opening) for maximum power transfer from electron beam to screen phosphors with no energy spillage onto the slot mask.
Although it was possible to use existing round phosphor gun technology with the CROMACLEAR CRT, a certain percentage of electron power would have been lost, thereby degrading overall image focus. An effective visual to describe this phenomenon is a “round peg, square hole” analogy: while contact might be taking place, it not completely precise. Excess energy transfer could lead to a warped grille or mask, resulting in possible image degradation (color purity and/or brightness uniformity problems). This mismatch tends to occur in aperture grille CRTs (stripe grille/circular electron beam). On the other hand, dot trio CRTs match a circular beam to a circular shadow mask.
This combination of dynamic beam focus and new electron guns also reduces the need for end-user moir and convergence controls.
Contrast: The term “contrast” has a unique role in overall image quality. Technically speaking, contrast refers to the use of opposing elements, such as colors, in proximity to opposites. Applying this definition to CRT-based monitors, contrast provides the appearance of depth to related objects. A good example is an illustration that provides highly defined, detailed image quality, such as a black ball resting on a white floor.
Contrast has a symbiotic relationship with overall CRT brightness: the higher the overall CRT brightness, the better the overall image contrast. As such, high contrast images cannot be achieved on CRTs with poor light output. These high levels are fundamental bases for the CROMACLEAR CRT.
Color saturation: Another subjective portion of overall image quality is color saturation. Colors appear differently to each end-user, making this a difficult specification to quantify. However, lack of meaningful numerical data does not prevent making a decision on which CRT type displays color in the best manner. Low-quality CRTs display colors in muted and blanched tones that are noticeable to the end-user. A high-quality tube like the CROMACLEAR CRT provides highly saturated, vivid colors.
Again, CROMACLEAR CRT color saturation levels work in combination with the other components to provide better overall image quality.
Convergence
Convergence is the process of controlling the CRT beam deflection to keep the red, green and blue beams properly overlapped when scanning the raster (area illuminated by the scan lines on a CRT). As the electron gun scans across the screen, the shape of electron beams slightly varies as the beam reaches the outer edges of the screen. Misconvergence, the technical term used when this process is not completely accurate, appears as color fringing on the edge of an image displayed on the screen. For example, a CRT monitor with misaligned electron beams will show a white “H” on a black background with one of the primary or secondary colors shadowing its edges. CROMACLEAR CRTs provide numerous deterrents to misconvergence, including the ELA guns and their tight mask pitch.
CromaClear vs Aperture Grille CRTs
Aperture grille CRT monitors currently use damping wires to hold the black striping in place between the phosphors. Comparatively, CROMACLEAR CRTs utilize a shadow mask that does not require the use of damping wires. Often, damping wires are visible to the user and mechanically obstruct the flow of the electron beams, critical to maximizing image focus. Without damping wires, the electron guns of a CROMACLEAR CRT hit the phosphors more consistently on all areas of the CRT.
In addition, damping wires are highly sensitive and are more susceptible to shipping damage. They also have the potential to be affected by harmonic distortion when speakers are placed near the CRT.
CromaClear vs Dot Trio CRTs
CROMACLEAR CRTs improve upon the image sharpness and focus attributed to dot trio CRTs. The slot mask design and illuminated phosphor alignment provide a tighter mask pitch, leading to improved image quality. In addition, the tighter mask pitch and ELA guns furnish sharper focus, while at the same time combating possible moir.
External links
NEC Display Site
ChromaClear white paper
Categories: Cathode ray tubeHidden categories: Orphaned articles from February 2009 | All orphaned articles | NPOV disputes from December 2007 | All NPOV disputes
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