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3-1
3. OPTICAL SYSTEM
3-1. Configuration
Lamp
unit
Mirror
box
unit
Prism
unit
Projec-
tion
lens
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Name
UHP lamp
Parabolic
reflector
UV IR filter
Multi-lenses
A, B
Polarization
light beam
splitter (PBS)
Phase
difference
plate
Condenser
lens
Dichroic
mirror
Full reflection
mirror
Field lens
Relay lens
Incident side
polarized
plate/Phase
difference
plate
Liquid crystal
panel
Cross prism
Projection
lens
Description
Light source of the optical system. AC lighting system 120W, arc length 1.3 mm.
As the arc length is shorter than the conventional metal halide lamp, the light source
operates as an ideal light point source and this improves the light convergence factor.
Also, the color temperature gets higher and this allows to reproduce more natural
white color.
Parabolic reflector converges light emitted from the UHP lamp forward in approximate
parallel light beams and illuminates the liquid crystal panel.
Optical filter to pass necessary visible rays and cut unnecessary ultraviolet rays and
infrared rays among light emitted from the UHP lamp.
Two multi-lenses A and B allow a circular beam light emitted from the light source to
illuminate the square liquid crystal panel evenly, thus providing projected pictures
with less brightness variation.
Separates the illuminating light from the light source into P polarization light and S
polarization light and leads both light to the multi-lens B with a little angle.
Converts the polarization direction of incident light via the multi-lens B into another
direction. Here, P polarization light waveform separated by PBS is converted into
another S polarization light waveform.
Converges the illuminating light emitted from the light source into the liquid crystal
panel.
Separates the white light emitted from the light source into RGB three primary colors.
The white light emitted from the light source reflects B light using a dichroic mirror 1
and the RG lights pass through the dichroic mirror 1. Of the RG lights passed, G light
is reflected by the dichroic mirror 2 and R light passes.
Reflection mirror to lead the R and B lights separated by the dichroic mirrors 1 and 2
to the liquid crystal panel.
Light transmitted through liquid crystal panel is converged in direction of focal point
and effectively entered entrance pupil of the projection lens.
In the R axis optical path which is longer than those of G, B, the relay lens works as
a correction lens to arrange the illumination distribution of the liquid crystal panel
surface with that of other liquid crystal panel.
The illumination lights separated into RGB have the S polarizing waveform compo-
nent in processing the PBS and phase difference plate operation previously de-
scribed.
The incident side polarized plate arranges the illumination light more effective direct
polarizing waveform. The phase difference plate used works to converge the S
polarizing waveform into the P polarizing waveform which fits to the transparent axis
of the liquid crystal panel.
Since the phase difference plate possesses the wavelength characteristics for light,
each RGB axis employs exclusive phase difference plate. These polarizing plates
and difference plates are constructed in one plate by attaching each other, and put
on a glass plate.
To increase the color purity ratio of three primary colors, the glass plate possess the
dichroic filter characteristics for RG axis.
Light exit side polarized plate is put on the light exit plane. When no signal voltage is
applied, the polarization direction of transmission light rotates by 90 degrees. When a
voltage is applied, the polarization direction is controlled owing to the voltage
applied. That is, the liquid crystal panel employs such general TN type liquid crystal.
In this model, the incidence/exit polarization plate is placed (in normally white mode)
so that the light transmission amount becomes maximum (white) when no voltage is
added and the light transmission amount becomes minimum (black) when maximum
voltage is added.
According to the liquid crystal panel specification, exclusive panel for each RGB axis
is employed and shown by identification seals.
Works to mix RGB lights passed through the liquid crystal panel.
Demodulated by the video signal on the liquid crystal panel and projects pictures
displayed on the liquid crystal at a screen. Light axis of the projection lens is set at
upper side of center of the liquid crystal panel and this realizes easy viewing of the
panel because the projected screen position is upper than the unit position. The
projected light shows S polarizing waveform and is compatible with the polarizing
screen.
The projection lens employs the zoom & focus system and allows to project enlarging
a picture upto maximum approx. 300 inch.