Optics: image projectors – Lamp control
Reexamination Certificate
2002-12-27
2004-08-31
Adams, Russell (Department: 2851)
Optics: image projectors
Lamp control
C353S119000, C353S052000, C353S057000
Reexamination Certificate
active
06783248
ABSTRACT:
TECHNICAL FIELD
The present invention is related to an image display apparatus for enlarging and projecting an image and picture on an image displaying element such as a liquid crystal projector, DLP projector, and a rear projection TV.
BACKGROUND ART
Referring to
FIGS. 14
to
14
, an explanation is made for a projector as one example of the image display apparatus such as a liquid crystal projector, DLP projector, and rear projector for enlarging and projecting still images and moving images from a personal computer, as well as video image or TV pictures from a video camera or video recorder.
FIG. 14
is a perspective view illustrating an arrangement of parts of a prior projector without a cabinet (but indicated by dotted lines).
FIG. 15
is a top view illustrating the part arrangement within the projector of FIG.
14
.
FIG. 16
illustrates a structure of a lamp house fitted within the same projector.
FIG. 17
is a circuit block diagram of the same projector.
The image display apparatus (projector)
1
PA includes a cabinet
2
, an image display
3
, the lamp house
4
, a projection lens
5
, a power supply
6
, an ignitor module
7
, a lighting device
8
, a signal processing unit
9
, a plurality of forced-air cooling fans
10
, and an input filter
11
.
The cabinet
2
forms a case which covers the whole projector, and is provided with the signal processing unit
9
extending on back and top of the cabinet
2
except for the lamp house
4
.
The image display apparatus
1
PA is connected to an AC mains
26
through an AC input cable
16
. The AC input cable
16
is connected to the power supply
6
through the input filter
11
. The voltage of the AC mains is, for example, 100 to 240 AC Volts, which is converted at the power supply
6
into DC voltages, such as DC 370 V, DC 12 V, DC 5 V, DC 3.3 V.
Connected to the power supply
6
are the signal processing unit
9
and the lighting device
8
. The image display
3
is connected to the signal processing unit
9
. The image display
3
includes an image displaying element
3
a
formed as a liquid crystal display or DMD element, and an optical system composed of a condenser lens and a prism (not shown) for focus control of a light from the discharge lamp
13
. The image displaying element
3
a
receives an image signal output from the signal processing unit
9
to give the resulting image which is projected by means of a light from the discharge lamp
13
of which focus is controlled by the above optical system.
The lighting device
8
is connected to the lamp house
4
. In detail, the lamp house
4
includes a high intensity discharge lamp
13
, a reflector
13
, and a lamp socket
14
b
(see FIG.
16
). The discharge lamp
13
such as a metal halide discharge lamp and super high pressure mercury discharge lamp (refer to Japanese Patent Publication Nos. 2-138561 and 6-52830 for example) is connected to the lighting device
8
through high voltage lead wires
12
and the lamp socket
14
b
. The lamp house
4
, which is detachable to the projector so that the user or operator can replace the discharge lamp
13
, is partly or entirely made of a resin. Numeral
42
in
FIG. 16
indicates a fixture of the reflector
30
.
The projection lens
5
receives the light from the discharge lamp
13
through the image display
3
in order to enlarge and project the image or picture given to the image display
3
.
The power supply
6
includes a rectifier
6
a
, a controller
6
b
, a boosting chopper circuit
6
c
, and four DC output circuits
6
d
to
6
g
. The rectifier
6
a
converts the input AC voltage into the DC voltage. The controller
6
b
controls the boosting chopper circuit
6
c
. The boosting chopper circuit
6
c
includes an inductance L
1
, a MOSFET (Q
1
), a diode D
1
, and a smoothing capacitor C
1
to output a DC voltage boosted to a desired level by switching the MOSFET (Q
1
). The DC output circuits
6
d
to
6
g
are respectively DC-DC converters which convert the output of the boosting chopper circuit
6
c
into desired DC voltages for supplying the same to the corresponding units. The DC output circuits
6
d
to
6
f
supply appropriate DC voltages to the signal processing unit
9
, while the DC output circuit
6
g
supplies an appropriate DC voltage to the lighting device
8
.
The lighting device
8
includes a controller
8
a
, a step-down chopper
8
b
, a polarity inverting circuit
8
c
, resistors R
2
, R
3
for lamp voltage detection, and a resistor R
4
for lamp current detection. The controller
8
a
is supplied with a DC output from the DC output circuit
6
g
through a capacitor C
7
so as to control the step-down chopper
8
b
and the polarity inverting circuit
8
c
based upon the lamp voltage and the lamp current respectively monitored by lamp voltage detection resistors R
2
, R
3
and the lamp current detection resistor R
4
. The step-down chopper
8
b
includes a MOSFET (Q
2
), a diode D
2
, an inductance L
3
, and a capacitor C
3
to step-down the input DC voltage supplied through a noise filter composed of an inductance L
2
and a smoothing capacitor C
2
for stably providing the electric power necessary to the discharge lamp
13
by switching the MOSFET (Q
2
). The polarity inverting circuit
8
c
, composed of MOSFETs (Q
3
to Q
6
), inverts the polarity of the DC output of the step-down chopper
8
c
by switching MOSFETs (Q
3
, Q
6
) alternately with MOSFETs (Q
4
, Q
5
), thereby providing an AC power to the discharge lamp
13
.
The ignitor module
7
includes a resistor R
1
, capacitors C
4
to C
6
, a sidac SSS, transistors T
1
, T
2
, a diode D
3
, and a spark-gap (GAP). The ignitor module
7
derives its operating voltage from the output voltage of the step-down chopper circuit
8
b
within the lighting device
8
so as to apply high voltage pulses (for example, 18 kVo-p) between electrodes of the discharge lamp
13
, bringing about a breakdown to thereby start lighting the lamp.
The signal processing unit
9
is connected at its input end to the personal computer, video recorder or the like through a signal cable
17
, and at its output end to the image displaying element
3
a
of the image display
3
. The signal processing unit
9
receives an RGB signal or TV signal from the computer, video recorders or the like connected to the signal cable
17
, and outputs a signal for displaying the image on the image displaying element
3
a.
The forced-air cooling fans
10
are provided for avoiding a temperature rise of the heat-generating parts within the image display apparatus
1
, and disposed respectively adjacent to the ignitor module
7
, the power supply
6
, and the lamp house
4
.
The operation of the ignitor module
7
will be now explained in detail.
The ignitor module
7
operates on the output voltage from the step-down chopper circuit
8
b
, which charges capacitor C
4
through resistor R
1
so that sidac SSS become conductive to release the electric charges accumulated in capacitor C
4
when capacitor C
4
is charged to a break-over voltage of sidac SSS.
At this occurrence, a transient voltage is caused by a transient phenomenon in combination with an inductance as viewed from the primary side of the transformer T
1
, and is transferred to the secondary side of transformer T
1
, followed by being rectified to accumulate charge in capacitor C
5
. This action is repeated to increase the charged voltage across capacitor C
5
. When capacitor C
5
is charged to the break-over voltage of the spark-gap (GAP), the spark-gap (GAP) conducts to discharge the capacitor C
5
. Upon this discharging, a voltage developed by a transient phenomenon in combination with an inductance as viewed from the primary side of transformer T
2
, is boosted at transformer T
2
and is then output as high voltage pulses.
A recent technical problem for the projector concerns with a light-and-compact design for portability.
In making the projector compact, it is noted that the ignitor module
7
for igniting the light source of the discharge lamp
13
generates high voltage pulses which, as shown in
FIG. 18
, inclu
Adams Russell
Koval Melissa J
Matsushita Electric & Works Ltd.
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