JVC DLA-G20 Sales Manual page 15

Projection type (front projection)
Screen reflectivity and recurrence
Reflectivity means that the light reflects in the direction
opposite to the angle of incidence.
Recurrence means that the light reflects in the
same direction as the angle of incidence.
The projector installation position must be changed
depending on the screen type. Position the projector so
that the reflected light is level with the audience's eyes.
Care should be taken to ensure that seats are not
darkened (within the angle of visibility).
Screen gain
The screen shows an image by reflecting the projected
light. This reflection degree is expressed with the gain
(= Gs). The standard screen gain reference is based on
the white screen which is set to "gain = 1".
(Strictly speaking, full diffusion (object obtained by burning
magnesium on a aluminum plate) is "gain = 1". In actual
use, "Kodacolor standard white" is "gain = 1". Normally,
"gain" means the peak gain. The peak gain is the value at
the point where the gain is the highest. )
The higher the gain, the brighter the screen. On the
other hand, the angle of visibility becomes narrower. Refer
to the typical example showing the relationship between
the gain and angle of visibility shown on the right. In
general, the angle of visibility is shown with the half gain
angle (= angle a: point where the peak gain is halved) and
1/3 gain angle (= angle b).
Gain = 1 Gain = 2.4
Note on using a sound screen
A sound screen is designed so that sound from the
speakers behind the screen passes through the screen
through numerous small holes at the regular pitch on the
screen surface.
With the D-ILA device, pixels are regularly arranged.
Therefore, a moiré phenomenon may be produced by
26
Reflectivity Recurrence
White, pearl, silver, Beads
polarized light (JVC Fine Screen Pro)
Incident light
Incident light
Reflected light
Reflected light
Screen
Screen
Screen gain chart
Beads screen
2.0
White screen
Screen gain
1.0
Pearl screen
0
60˚ 50˚ 40˚ 30˚ 20˚ 10˚ 0˚ 10˚ 20˚ 30˚ 40˚ 50˚ 60˚
Angle of visibility
(Left) (Right)
a = 1/2 Peak gain
b = 1/3 Peak gain
b = 38 degree
Audience area
interference from these screen holes. The extent of this
phenomenon depends on the hole diameter, hole
disposition, hole disposition pitch and projection size. As
there is no way to calculate this effect beforehand, be sure
to verify the effect with a test projection.
FINE SCREEN PRO
Fine beads screen (Quick Facts)
Q.
Is the fine beads screen the same as the beads type?
If so, since the beads type has a sharp gain, does the
screen seem darker to viewers at the edge of the visibility
angle?
A.
As you can see the gain chart shown below, the absolute
value indicates that the fine beads screen is brighter at
most angles and the gain is higher even at the edges than
any other screen type except for the white screen. All
viewers will see a very bright picture, but since peak is
sharp, the screen will be darker for people on the edges
than for those in the middle.
To show the angle of visibility, there is a scale called
the half gain angle (angle a). Depending on the case, the
half gain angle of the fine beads screen may be narrower.
Screen gain chart
Beads screen
2.0
Fine screen
White screen
1.0
Pearl screen
0
60˚ 50˚ 40˚ 30˚ 20˚ 10˚ 0˚ 10˚ 20˚ 30˚ 40˚
(Left) (Right)
Angle of visibility
• The screen gain charts except for the Fine Screen Pro are shown as a guide.
Projection type (front projection)
However, the absolute value for the gain at all angles is
higher in many cases. Therefore, it is risky to select a
screen on the basis of its angle of visibility alone. We
recommend comparing screens with the gain chart.
With the fine beads screen, beads with a diameter
almost half that of conventional beads (70 µm) are
embedded in a high density layout. This eliminates stray
light and ringing phenomena, achieving an excellent
picture with clear color reproduction and high contrast.
When brightness or picture quality is important, it is better
to choose the fine beads screen.
Fine beads screen
Angle of visibility Screen gain
0˚ 2.40
5˚ 2.21
0˚ 1.91
15˚ 1.50
18.5˚ 1.20
(Angle a)
20˚ 1.11
25˚ 0.94
30˚ 0.86
35˚ 0.82
38.0˚ 0.80
(Angle b)
40˚ 0.79
50˚ 60˚
45˚
0.77
27