n
Role of the lens
Fresnel lens
With the Fresnel lens cut in the form of circles as shown on the upper left, the light axis is directed inward (shown in the
middle and right figures) to prevent loss of brightness at the corners of the screen. This minimizes shadows and ensures
that uniform brightness is obtained throughout the screen area.
Lenticular lens
With a lenticular lens which is cut straight vertically and horizontally as shown in the upper left and middle figures, the
viewing angle is determined (upper right figure) and gain is held on the screen. The vertical lenticular determines the
viewing angle in the horizontal direction and the horizontal lenticular determines the viewing angle in the vertical direction.
33
As discussed in the section on front screens, the screen is an important factor in determining the final quality of the system.
It is necessary to understand the features of the various types of screens.
Rear screens are roughly divided into “hard” and “soft” types. ”Hard” is further classified into several types. The
representative types are shown below.
As of February, 1999 O: Good : Normal
2
: Care required
Total market (includes mirrors which the Projection Sales Department does not handle)
Types of rear screen
The cost is relatively low and a bright, high-quality picture can be obtained.
Some shadows may occur.
Large size screens are difficult to transport and deliver.
Color shift is minimized.
Brightness levels are good.
There are joints in the screen.
As the light passes through two screens, resolution tends to be degraded.
Large size screens are difficult to transport and deliver.
Expensive but well suited for large screens.
(Can be broken down for transportation. Joints may be visible.)
As the light passes through two screens, resolution tends to be degraded.
If the throw distance is short, the following phenomena result.
(As the light axis compensation is insufficient, shadows appear.)
At the cross section of the lenticular, scintillation may occur.
Large size screens are difficult to transport and deliver.
This is relatively inexpensive.
Shadows and color shifts may be noticeable.
Contrast is excellent.
Picture is not very bright.
Large size screens are difficult to transport and deliver.
This is relatively inexpensive.
Shadows and color shifts may be noticeable.
Transportation, delivery and construction are easy.
The screen moves with the air flow.
Picture is not very bright.
Soft
Hard
Type
Single Fresnel lenticular
Double Fresnel lenticular
Double cross lenticular
Dispersal agent hard type
Dispersal agent soft type
Maximum size
150 model (4:3)
150 model (4:3)
200 model (4:3)
250 model (16:9)
180 model (16:9)
1000 model (4:3)
Characteristics
Single
Fresnel lenticular
Double
Fresnel lenticular
Single
cross lenticular
Double
cross lenticular
With dispersing agent contained
Hard
Soft
Brightness (gain)
Viewing angle
Contrast
Luminance uniformity (shading)
Color uniformity
Color reproduction
Resolution
Scintillation
Hot spot (fire ball)
Flare (blot)
Throw distance
Shock strength
Flatness
Installation difficulty
Change in resolution due to “floating”
Durability against environment
Maintenance
Maximum size (model)
V
V
V
~
V
V
V
V
V
V
~
V
V
V
V
V
V
V
V
150 (4 : 3)
V
V
~
V
V
~
V
V
V
V
V
~
V
V
V
V
V
150 (4 : 3)
~
V
V
V
~
V
V
V
~
V
V
~
V
V
V
V
2
250 (16 : 9)
~
V
V
V
V
V
2
2
~
V
V
V
V
V
V
250 (16 : 9)
2
2
V
V
2
~
V
V
V
V
V
V
V
180 (16 : 9)
2
2
V
V
2
~
V
2
V
V
2
V
1000 (4 : 3)
D-ILA Method Present Condition and Subject
32
Basic facts about rear screens
n
Terminology
Single/double:
Shows the number of screens to be used to produce one screen
Single: one, double: two
Fresnel:
Fresnel lens which is cut in the form of a concentric circuit.
Lenticular:
Lens cut straight vertically and horizontally.
Cross lenticular:
Lenticular lens cut vertically and horizontally so that cut lines are crossed. Processing is not possible
on the same surface. So, for a single lens, the front and rear sides are cut. For double lens, one
side of each lens is processed.
Dispersal agent:
This disperses the light and looks like frosted glass. This is mixed into material or sandwiched
between the screen surfaces.
<Cost>
A single screen can cost several million yen and a double
screen will cost several times more (for the size, refer to
the next page).
A mold is used to manufacture a single screen. A double
screen is manufactured by cutting each screen individually.
(Large single screens are also manufactured by cutting, so
they are also expensive.)
<Screen delivery>
As a hard screen cannot be rolled like a soft screen, it is
delivered to the installation location in finished form.
Therefore, it is necessary to ensure a delivery path. If the
delivery path cannot be maintained after a building is
completed, the screen must be delivered during
construction.
Projection type (rear projection)
Projection type (rear projection)
Summary of Contents for DLA-G20
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