Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
2001-04-04
2003-11-11
Adams, Russell (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C353S033000, C353S034000, C353S037000, C353S084000, C349S008000
Reexamination Certificate
active
06644812
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a display apparatus, for example, a projection type display apparatus used to display a computer image or a video image on a large screen.
2. Related Background Art
In recent years, the use of display apparatus has been diversified in the field of image processing or the like and therefore, there have been required display apparatuses in which optimum color purity, color balance, illuminance, etc. are obtained in accordance with the use.
FIG. 24
of the accompanying drawings show the construction of a projection type display apparatus according to the prior art. In
FIG. 24
, white light emitted from a light source portion
1
passes through fly-eye lenses
3
,
4
, a PS conversion element
5
, a condenser lens
6
, etc., whereafter the light in the red band is transmitted through a dichroic mirror DM
1
and the lights in the green to blue bands are reflected by the dichroic mirror DM
1
. Generally, as the light source, use is made of a halogen lamp, a metal halide lamp, a super-high pressure mercury lamp or the like, and as a color separating and combining optical element, use is made of a dichroic mirror, a dichroic prism or the like.
The red band light transmitted through the dichroic mirror DM
1
exhibiting the spectral transmittance shown in
FIG. 25A
of the accompanying drawings has its optical path changed by 90° by a total reflection mirror M
1
, and enters a liquid crystal display element
8
R through a field lens
7
R and a trimming filter TR exhibiting the spectral transmittance shown in
FIG. 25C
of the accompanying drawings, and is light-modulated there in conformity with an input signal. The light-modulated light enters a dichroic prism
9
, and has its optical path changed by 90° by the dichroic prism
9
and enters a projection lens
10
.
On the other hand, the green-blue band light reflected by the dichroic mirror DM
1
and having had its optical path by 90° enters a dichroic mirror DM
2
exhibiting the spectral transmittance shown in
FIG. 25B
of the accompanying drawings. From
FIG. 25B
, the dichroic mirror DM
2
has the characteristic of reflecting the green band light and therefore, the green band light is reflected there and has its optical path changed by 90°, and enters a liquid crystal display element
8
G through a field lens
7
G and a trimming filter TG exhibiting the spectral transmittance shown in
FIG. 25D
of the accompanying drawings, and is light-modulated there in conformity with the input signal. The light-modulated green band light enters the dichroic prism
9
and the projection lens
10
in the named order.
The blue band light transmitted through the dichroic mirror DM
2
enters a liquid crystal display element
8
B through the intermediary of a condenser lens
11
, relay lens
12
, field lens
7
B and total reflection mirrors M
2
and M
3
, and is light-modulated there in conformity with the input signal. The light-modulated blue band light enters the dichroic prism
9
, and has its optical path changed by 90° by the dichroic prism
9
and enters the projection lens. In the prior-art projection type display apparatus constructed as described above, when the contrast of each liquid crystal display element is sufficiently high, the color purity of the red band light is determined by the spectral characteristic of the source light and the spectral transmittances of the dichroic mirror DM
1
and the trimming filter TR, the color purity of the green band light is determined by the spectral characteristic of the source light and the spectral transmittances of the dichroic mirror DM
1
, DM
2
and the trimming filter TG, and the color purity of the blue band light is determined by the spectral characteristic of the source light and the spectral transmittances of the dichroic mirrors DM
1
and DM
2
.
As described above, in the construction of the prior-art projection type display apparatus, the design of each optical element has been made such that optimum color balance and color purity are obtained.
However, depending on the use of the projection type display apparatus, there are various requirements such as a case where bright display is required even if the apparatus becomes bulky, a case where bright display is required even if color purity is reduced, and a case where color purity is unnecessary in a black-and-white mode.
In the conventional projection type display apparatuses, in order to enhance color purity, a light having a wavelength of 570 nm-600 nm has been cut to thereby obtain optimum color balance and color purity, but in the case of many lamps, the peak exists in the vicinity of 580 nm in terms of spectral distribution. When a wavelength in the vicinity of this is used, it becomes possible to improve illuminance.
As such an example, mention may be made of a projection type display apparatus described in Japanese Patent Application Laid-Open No. 7-072450. In the description of this publication, there is proposed a projection type display apparatus having in an optical path optical elements differing in spectral characteristic, and provided with a mechanism for retractably inserting the optical elements. Thereby, display giving priority to brightness or display giving priority to color reproducibility can be realized by an apparatus, but when the optical elements are inserted to thereby effect the display giving priority to color reproducibility, the light in the entire wavelength range or the two-color wavelength range is transmitted through the optical elements, and since the optical elements are band cut filters, the transmittance of the wavelength necessary for projection is low, and this has led to the problem that the display becomes darker than necessary.
In order to solve this problem, Japanese Patent Application No. 1-235479 is mentioned as an example in which a moving third optical element is disposed at a place where only the red or green wavelength range is transmitted and an edge filter is used as the optical element, whereby the transmittance of the wavelength necessary for projection is high and the reduction in the quantity of light during the display giving priority to color reproducibility is made as small as possible, but in this case, there arises the problem that the brightness and color taste when priority is given to color reproducibility are changed by the unevenness of the cut wavelength in the manufacture of a dichroic mirror for dividing the light into the red band light and the green band light. At the same time, there has also arisen the problem that with the unevenness of the brightness of the display giving priority to color reproducibility, the up rate of brightness of the case where priority is given to brightness to the case where priority is given to color reproducibility becomes uneven.
Describing this in detail, assuming that the brightness of the lamp itself is not uneven, the absolute value of the brightness in the case of the display giving priority to brightness is constant because the spectral distribution of the lamp is intactly utilized. However, as regards the brightness when priority is given to color reproducibility, light of 570 nm-600 nm cut to enhance the color purity thereof is changed to e.g. 565 nm-600 nm or 575 nm-600 nm by the unevenness of the cut wavelength in the manufacture of the dichroic mirror and therefore, the brightness and color taste in the case of the display giving priority to color reproducibility become uneven. Along therewith, the up rate of brightness of the case where priority is given to brightness to the case where priority is given to color reproducibility becomes uneven.
Japanese Patent Application Laid-Open No. 7-318883 and Japanese Patent Application Laid-Open No. 9-211449 may be mentioned as examples in which the unevenness of brightness and color taste due to such unevenness of the cut wavelength in the production of the dichroic mirror is restrained by the use of a dichroic mirror subjected to inclination correction moving in a direction parallel to a direction in whi
Kodama Hiroyuki
Okuyama Atsushi
Adams Russell
Cruz Magda
Morgan & Finnegan
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