Why Does the Intensity Appear So Non-Uniform in Bright Areas?
Actually, the intensity variation is likely to be even worse than you might think – possibly as much as 2:1 from the center to the corners. In most cases you do not notice it. With large deflection angle tubes, fewer electrons make it to phosphor dots near the edge of the screen. It is simple geometry. (From: Bob Myers (myers@fc.hp.com).) It is extremely difficult for any CRT display to maintain perfect brightness and color uniformity across the entire image. Just the geometry of the thing – the change distance from the gun to the screen as the beam is scanned, the changing spot size and shape, etc. – makes this nearly impossible, and there can also be variations in the phosphor screen, the thickness of the faceplate, etc.. Typical brightness-uniformity specs are that the brightness won’t drop to less than 70% or so of the center value (usually the brightest spot on the screen). On color tubes, the lack of perfect brightness uniformity is aggravated by the lack of perfect COLOR uniform
Actually, the intensity variation is likely to be even worse than you might think – possibly as much as 2:1 from the center to the corners. In most cases you do not notice it. With large deflection angle tubes, fewer electrons make it to phosphor dots near the edge of the screen. It is simple geometry. (From: Bob Myers (myers@fc.hp.com).) It is extremely difficult for any CRT display to maintain perfect brightness and color uniformity across the entire image. Just the geometry of the thing – the change distance from the gun to the screen as the beam is scanned, the changing spot size and shape, etc. – makes this nearly impossible, and there can also be variations in the phosphor screen, the thickness of the faceplate, etc.. Typical brightness-uniformity specs are that the brightness won’t drop to less than 70% or so of the center value (usually the brightest spot on the screen). On color tubes, the lack of perfect brightness uniformity is aggravated by the lack of perfect *color* unifo
Actually, the intensity variation is likely to be even worse than you might think – possibly as much as 2:1 from the center to the corners. In most cases you do not notice it. With large deflection angle tubes, fewer electrons make it to phosphor dots near the edge of the screen. It is simple geometry. (From: Bob Myers (myers@fc.hp.com)). It is extremely difficult for any CRT display to maintain perfect brightness and color uniformity across the entire image. Just the geometry of the thing – the change distance from the gun to the screen as the beam is scanned, the changing spot size and shape, etc. – makes this nearly impossible, and there can also be variations in the phosphor screen, the thickness of the faceplate, etc.. Typical brightness-uniformity specs are that the brightness won’t drop to less than 70% or so of the center value (usually the brightest spot on the screen). On color tubes, the lack of perfect brightness uniformity is aggravated by the lack of perfect *color* unifo
Actually, the intensity variation is likely to be even worse than you might think – possibly as much as 2:1 from the center to the corners. In most cases you do not notice it. With large deflection angle tubes, fewer electrons make it to phosphor dots near the edge of the screen. It is simple geometry. (From: Bob Myers (myers@fc.hp.com)). It is extremely difficult for any CRT display to maintain perfect brightness and color uniformity across the entire image. Just the geometry of the thing – the change distance from the gun to the screen as the beam is scanned, the changing spot size and shape, etc. – makes this nearly impossible, and there can also be variations in the phosphor screen, the thickness of the faceplate, etc.. Typical brightness-uniformity specs are that the brightness won’t drop to less than 70% or so of the center value (usually the brightest spot on the screen). On color tubes, the lack of perfect brightness uniformity is aggravated by the lack of perfect COLOR uniform
