Projection Type (Rear Projection) - JVC DLA-G20 Sales Manual

Projection type (front projection)
Polarized light screen (Quick Facts)
Principle of the polarized light screen
Lights used for normal illumination include a component
which oscillates in all directions (360˚) to distribute the
light. The light emitted from the DLA-G20 D-ILA multime-
dia projector, on the other hand, mainly consists of verti-
cally oscillating light. A screen with polarized light charac-
teristics reflects only "vertically oscillating light" and
absorbs "horizontally oscillating light". JVC polarized light
screens include the SF-L100FJ, SF-L060SJ, and SF-
L080S.
When the DLA-G20 projects light onto this type of
screen, most of the light is reflected because the light from
the DLA-G20 consists mainly of vertical components.
Since external light, on the other hand, consists of both
horizontal and vertical components, the screen will absorb
up to 50 percent of the external light, reflecting only the
vertical components. As a result, high contrast can be
maintained even in a bright environment.
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Notes on the use of the polarized light screen
1. To obtain the proper effect with the polarized light
screen, the polarized direction of the projector must be the
same as that of the screen. If a projector with a different
polarized direction is used, (for example, a projector that
outputs "horizontally oscillating light"), most of the
projected light will be absorbed on the screen surface and
the picture will not be visible.
For the DLA-G20/15, only the following screens should be
used: SF-L100FJ / SF-L060FJ / SF-L060FSJ / SF-L080S.
If any of these screens are used with another brand of
projector or the DLA-G20/15 is used with another brand of
screen, be sure to check the polarized light screen effect.
2. With a CRT projector or DLP system projector which
does not output a polarized light, a polarized light screen
effect cannot be obtained.
3. Some high-intensity LCD projectors may not be used
with a polarized light screen.
Theoretically, a
polarizing screen
External light reflection,
provides the same
• "horizontally oscillating light" is
effect that would be
shut out with a polarizing film
and does not pass through.
obtained by cutting the
• "vertically oscillating light" is reflected.
external light reflection
Only half of the
in half. In other words,
external light is reflected.
the polarized screen
can provide the same
contrast as a normal
screen in a room that's
Projector light reflection
twice as bright.
• "vertically oscillating light" is reflected.
All light is reflected
• Reflection surface
• Polarizing film
(Both are adhered to the product.)
• The arrow mark showing the light in the figure on the left does not show
the light oscillating direction. The amount of the reflected light is
generalized.

Projection type (rear projection)

Rear projection
With rear projection systems, the transmitted light, rather
than the reflected light, appears on the screen as an
image. This means that the projector must be installed
behind the screen. In principle, rear projection is not
affected by the level of illumination in a room. If the D-ILA
is used as a rear projector, its powerful light output
ensures a clear, easy-to-view picture even in a very
brightly lit room.
(Nevertheless, even with the D-ILA projector, the less the
external light reflection, the better the image quality.)
(Refer to the table on page 10.)
Installation standard
For rear projection, basically use the DLA-S15 D-ILA multimedia projector.
During rear projection with the DLA-S15, the reference light axis should intersect with the screen (incident angle 0˚)
regardless of the type of the screen.
Installation example
(reflection in the vertical direction)
Viewed
from the side
Screen
Direct projection
Reference (Mirror)
light axis
One mirror
reflection projection
Viewed
from the above
Direct projection
Screen
(Mirror)
Reference
One mirror
light axis
reflection projection
Hard screens with a cut lens (see below) have a fixed
focus length. It is OK for the lens edge to be at the focus
length position. If the distance is not appropriate, select a
screen which allows the projector to be installed at a
distance that exceeds the screen focus length. If the
screen focus length and throw distance do not match each
other, there will be problems with the picture. These are
especially apparent if the projector is within the screen
focus length; hot spots and color shifts are very noticeable,
resulting in a significant loss of picture quality.
D-ILA Method Present Condition and Subject
The throw distance is the same as with front projection. In
general, the light axis is folded back with a mirror and the
depth of the back is reduced. To determine the
relationship of the positions of the projector, mirror and
screen, a CAD-based simulation is required.
Installation example
(reflection in the horizontal direction)
Viewed
from the side
Screen
Direct projection
Reference
(Mirror)
light axis One mirror
reflection projection
Viewed
from the above
Direct projection
Screen
(Mirror)
Reference
light axis One mirror
reflection projection
(A) Good (B) Bad (C) Reasonably good
L = Throw distance = Screen focus length
(A) L = Good
(B) L < Bad
Hot spots, color shifts, uneven brightness and blurred focus are
very evident. This setting should be avoided.
(C) L > Reasonably good
This setting is not the best, but better than L< .
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