JPH0389316A - Projection type video display system - Google Patents
Projection type video display systemInfo
- Publication number
- JPH0389316A JPH0389316A JP1226840A JP22684089A JPH0389316A JP H0389316 A JPH0389316 A JP H0389316A JP 1226840 A JP1226840 A JP 1226840A JP 22684089 A JP22684089 A JP 22684089A JP H0389316 A JPH0389316 A JP H0389316A
- Authority
- JP
- Japan
- Prior art keywords
- light
- projection
- polarizing plate
- polarization
- projection surface
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 230000010287 polarization Effects 0.000 claims abstract description 52
- 239000004973 liquid crystal related substance Substances 0.000 claims abstract description 30
- 238000005286 illumination Methods 0.000 claims abstract description 16
- 238000010586 diagram Methods 0.000 description 6
- 230000005684 electric field Effects 0.000 description 4
- 238000002834 transmittance Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
Landscapes
- Liquid Crystal (AREA)
- Projection Apparatus (AREA)
Abstract
Description
[産業上の利用分野]
本発明は投映型の映像表示システムに関し、より詳しく
は、会議、講演会、集合教育等における多数の出席者に
対して、コンピュータ、VTR等を用いて種々の情和を
提示し理解を促す為に用いられる投映型の映像表示シス
テムに関する。
[従来の技術]
近年、コンビエータの発展、普及は目ざましく、企業、
研究機関、教育機関等においても、文章1表、グラフ、
図形等の情報の作成、編集などにコンピュータが多用さ
れてきている。また、テレビジョン技術の発達により、
安価なVTR(ビデオテープレコーダ)やビデオカメラ
等が急速に普及し、動きを伴う種々の情報の提示として
動画像を用いることが多くなっている。
こうしたコンピュータによる文章、表、グラフ、図形等
の情報や、ビデオによる動画像情報を、会議、講演会、
集合教育などの多数の出席者に対して提示し、理解を促
す為に投映型の映像表示装置が用いられてきている。
従来、この種の投映型映像表示装置は、典型的には%第
3図に示す如く構成されている。第3図において、30
はコ、ンビュータ、ビデオ等の文章、グラフ、図形、動
画像等の情報源であり、31は投映用光源、32は情報
21130からの情報が映像として再生される液晶パネ
ル、33は液晶パネル32上に再生された映像を光源3
1からの光を用いて投映面34に投映する投映レンズで
ある。
投映面34に表示された映像を観察するものと同じ側か
ら映像を投映する方式は前方投映型と呼ばれ、反対の側
から映像を投映する方式は背面投映型と呼ばれ、更に簡
易なものとしては、オーバーへラドプロジェクタの原稿
面上に液晶パネルを置いた構成のものも従来、多用され
てきている。
この様な投映型の映像表示装置に好適に用いられる液晶
パネルは、広く知られている如<、31114図の様に
構成されている。第4図において、液晶素子42は、印
加される電界の強さに応じて、透過する光の偏光特性を
変化させる機能を有し、液晶素子42を挾む様に設けら
れた上下の電極手段4°1.43は、情報源45からの
再生すべき映像信号に応じて、液晶素子42の網の目状
に分割された任意の場所(画素と呼ぶ)に任意の電界を
形成する。また、入射側偏光板40は投映用光源からの
投映光の偏光方向を一定の方向に揃える機能を有し、出
射側偏光板44は、液晶素子42を透過して来た光のう
ち、当該偏光板44と同一の偏光方向を有する光のみを
選択的に透過する機能を有している。
よって、液晶素子42の多数の画素のうち、透過光の偏
光方向が出射側偏光板44の配向方向と同一の方向とな
る如く上下の電極手段41.43によって選択的に電界
が印加された画素を透過する光のみが出射側偏光板44
から出射できることになり、このとき、情報源45から
の再生すべき映像信号によって各画素に印加される電界
は制御されているので、液晶パネル上に映像が再生され
る。尚。
この際、この映像光は出射側偏光板44の偏光方向と同
一の偏光方向を有・する。[Industrial Application Field] The present invention relates to a projection type video display system, and more specifically, the present invention relates to a projection type video display system, and more specifically, it displays various information using computers, VTRs, etc. to a large number of attendees at conferences, lectures, group education, etc. This invention relates to a projection-type video display system used to present and promote understanding. [Conventional technology] In recent years, the development and spread of combinators has been remarkable, and companies,
In research institutions, educational institutions, etc., text 1 table, graph, etc.
Computers are increasingly being used to create and edit information such as graphics. Also, with the development of television technology,
2. Description of the Related Art With the rapid spread of inexpensive VTRs (video tape recorders), video cameras, and the like, moving images are increasingly being used to present various types of information that involve movement. Computer-generated text, tables, graphs, figures, and other information, as well as video-based moving image information, can be used at conferences, lectures, etc.
Projection-type video display devices have been used to present information to a large number of participants in group education to encourage understanding. Conventionally, this type of projection type image display apparatus is typically constructed as shown in FIG. In Figure 3, 30
31 is a projection light source, 32 is a liquid crystal panel on which information from the information 21130 is reproduced as a video, and 33 is a liquid crystal panel 32. Light source 3
This is a projection lens that projects onto a projection surface 34 using light from 1. A method in which the image is projected from the same side as the one from which the image displayed on the projection surface 34 is viewed is called a front projection type, and a method in which the image is projected from the opposite side is called a rear projection type. Conventionally, overherad projectors with a liquid crystal panel placed on the document surface have also been widely used. A liquid crystal panel suitably used in such a projection type image display device is configured as shown in FIG. 31114, as is widely known. In FIG. 4, a liquid crystal element 42 has a function of changing the polarization characteristics of transmitted light according to the strength of an applied electric field, and upper and lower electrode means are provided to sandwich the liquid crystal element 42. 4° 1.43 forms an arbitrary electric field at an arbitrary location (referred to as a pixel) divided into a mesh of the liquid crystal element 42 according to the video signal to be reproduced from the information source 45. The input side polarizing plate 40 has a function of aligning the polarization direction of the projection light from the projection light source in a fixed direction, and the output side polarizing plate 44 has the function of aligning the polarization direction of the projection light from the projection light source in a certain direction, and the output side polarizing plate 44 has the function of aligning the polarization direction of the projection light from the projection light source in a certain direction. It has a function of selectively transmitting only light having the same polarization direction as the polarizing plate 44. Therefore, among the many pixels of the liquid crystal element 42, the pixels to which an electric field is selectively applied by the upper and lower electrode means 41, 43 so that the polarization direction of transmitted light is the same as the alignment direction of the output side polarizing plate 44 Only the light that passes through the output side polarizing plate 44
At this time, since the electric field applied to each pixel is controlled by the video signal to be reproduced from the information source 45, the video is reproduced on the liquid crystal panel. still. At this time, this image light has the same polarization direction as the polarization direction of the output side polarizing plate 44.
ところで、この種の投映型映像表示装置は、会議等の場
で用いられるものであるので。
出席者がメモ等の記録を行なえる様に、成る程度の照明
の下で使用する必要がある。しかし乍ら、上述従来例に
おいて、投映型映像表示装置に好適に用いられる液晶パ
ネルは、投映光強度が低い為、照明の下で使用すると見
えすらいという欠点がある。
このことを第5図を用いて、更に、説明する。同図にお
いて、50は液晶パネル上に再生された明画素の投映面
52上の像であり、その光の強度を工、とする。また、
51は液晶パネル上に再生された暗画素の投映面52上
の像であり、その光の強度をI。tとする、投映面52
上には、液晶パネルの投映光以外にも、照明光源からの
直接光(強度1o)や照明光源からの光の室内での反射
による間接光(強度ts)が入射する。
ここにおいて、直接光に比べて間接光は一般的に1/1
0以下であり(ここでは1/10とする)、液晶パネル
の明画素と暗画素の透過光強度比は一般的に10: 1
から50:l程度である(ここでは20:1とする)。
ここで、第1の場合として、室内照明を暗くし暗画素強
度11.と直接光強度Iゆとが等しいとすると、投映面
52上での明画素と暗画素の明るさの比すなわちコント
ラストはコントラスト=
となる。
(■。+Io +■。
−tl + I * + I a )” (2
0I−rr +I。
OIゎ 1/(x、rr
L / 10 I o )
= (20+1+1/10)/
1+l+1/10) 与10゜
この場合、
+1/1
+ ■。+
)/(I
成る程度のコントラスト
(
が得られるが、照明光が暗い為、出席者のメモ書き等に
は著しい不便を来すという問題がある。
次に、第2の場合として、室内照明を明るくし、明画素
強度!。と直接光強度!、が等しいとすると、投映面5
2上での明画素と暗画素の明るさの比は、
コントラスト= (t、s+te +Im ) / (
Isrr+j。+1.)
=(20I□g+20Iett+
21eer ) / (Istr +20I**r+2
I*rr)
=42/2341.8
となり、コントラストは著しく低下し、投映像は殆ど見
えないという問題が生じる。
上記問題点を解決する為、!1!1の場合と同じコント
ラストを得るべく、照明光強度は第2の場合のままとし
て投映光強度を何倍(k)すれば良いかを求めると、
10.5= (20・k ” 1eer +20 Ie
re+21stt ) / (k Iott
+2゜f net + 21 o’tt・)= 4
20に+lO+2)/ (k+20+2)
よりに=22となる。
すなわち、投映用光源の強度を22倍も強くする必要が
あることが分かる。投映用光源の強度を22倍も強くす
ると消費電力も22倍多くなり、光源の冷却等において
実用的でなくなるという重大な問題が生じることになる
。
従って、本発明の目的は、上記課題を解決すべく、上述
の種類の投映型映像表示システムにおいて、出席者がメ
モ等の記録を行なう為に充分な室内照明を行ないつつも
投映面上に良好なコントラストを持った像が得られる投
映型映像表示システムを提供することにある。
[課題を解決する為の手段]
上記目的を達成する本発明では、投映直に映像を投映す
る投映型映像表示システムにおいて、投映面に達する光
に第、1の偏光特性を持たせる為の第1の偏光手段と、
周囲を照明する為の照明光に上記第1の偏光特性と直交
する第2の偏光特性を持たせる為の第2の偏光手段と、
投映面に映像を表示する投映光に上記第1の偏光特性と
平行な偏光特性を持たせる為の第3の偏光手段が具備さ
れている。
[作用]
上記構成の本発明においては、室内照明用光源からの直
接光は投映面の偏光特性と興なる偏光特性を有する為に
投映面上に到達しない一方、投映光は投映面の偏光特性
と同じ偏光特性を有するので投映面に達し、これにより
周囲が明るいにも係らず投映面上のコントラストが改善
される。
【実施例1
第1図は本発明の第1実施例を説明する為の図であり、
図中、1は液晶パネルであり、これは図示しないコンピ
ュータ、ビデオテープレコーダ等の映像信号を再生する
。液晶パネルlで再生された投映光は・、投映光源3か
らの光によって投映レンズ2を介して投映面6上に投映
される。
また、第1図中、7は室内の照明用の光源、4は投映面
6に水平方向(図中矢印5で示す)の偏光特性を持たせ
る為の偏光板、8は室内照明光に偏光板4の偏光特性(
矢印5)と直角な方向の偏光特性(矢印9で示す)を持
たせる為の偏光板、11は室内照明光の直接光の偏光特
性を模式的に示すもの、13は室内照明光の間接光の偏
光特性を模式的に示すものである。
更に、液晶パネル1は投映光源3の光の入射側と出射側
の両側に偏光板を有しているので(第4図の説明参照)
、偏光板4の偏光特性と平行な偏光特性(矢印12で示
す)を有する出射側の偏光板の偏光特性に支配されてお
り、投映光の偏光特性は符号IOで模式的に示す様なも
のとなる。
以上の構成に基づく作用を説明する。液晶パネル1に再
生された映像は、投映光源3で照明され、投映レンズ2
により投映面6に投映されるが、このとき投映光は矢印
12で示す偏光特性により偏光板4と平行な偏光状態に
なっているので偏光板4を殆ど通過できる。
一方、室内の照明光源7からの直接光は偏光板8により
偏光板4と直角な偏光状態にされているので、偏光板4
を殆ど通過できない、室内の照明光源7からの光が室内
の種々の物体で乱反射して投映面6に入射する場合は、
乱反射によって間接光は特定の偏光特性を有さなくなっ
ている為、偏光板4を通過できる。
第1実施例において、偏光板4及び8として、偏光板と
同一の偏光方向の光の透過率が90%であり偏光板と直
交方向の光の透過率が1%であり、自然光(無偏光光)
の透過率が25%の偏光板を用い、液晶パネル1の明画
素と暗画素の強度比が、前記従来例の如く、20:]の
液液晶バネを用い、更に偏光板4及び8がない状態にお
いて・室内照明用光源7の直接光の強度が液晶パネルl
の明画素の強度と等しくなる様に設定する(間接光の強
度は前述した従来例における様に直接光のl/10とす
る)。
こうした設定条件(この条件は特別なものでなく一般的
である)で偏光板4,8等を用いた場合、投映面6上で
のコントラストは次の様になる。
コントラスト=(1,、+I。+Is ) / CI@
tt +Io +Ia )
= (201,tt xo、9+20
1*rt xQ、25XO,t+
2I□f Xo、25X0.2
5)/ (I。tt xQ、9+2
0■。tt xQ、25xO,1
+21att Xo、25XO。
25)
= (18+0.5+0.125
)/ (0,9+0.5+0゜
125)41・2.2
この値は、前記従来例において室内照明を暗くした場合
以上のコントラストとなり充分なものと言いつる。
こうして、it実施例によれば室内照明を充分に明るく
しつつ投映面6上のコントラストも充分なものとなしつ
る。
ここで、上記の如く室内照明は偏光板8の存在によって
明るさが25%に低下するので、室内照明光の強さを4
倍に上げた場合を考えてみる。
この場合、コントラストは、
コントラスト” (201−tt xQ、9+80ra
te xQ、25XO,1+
81 oee X O−25” ) / (Ierr
XQ、 9+80 ratexQ、25xO−1+8
I−r
、xo、252)
= (18+2+0.5)/ (Q
、9+2+0. 5) 辱6.0
となり、多少低下するが充分良好なコントラストが得ら
れる。
実際の動作においては、投映面6からの反射光は更に偏
光板4を介して見られる訳であり、この反射では偏光方
向は殆ど保存される為、投映光10は投映面6で反射し
た後90%近くの光が偏光板4を透過する。これに対し
、照明光は投映面6で反射後再び偏光板4で減衰する。
従って、実際に投映面6を見た場合のコントラストは上
記計算値以上に良好になる。
第2図は本発明の第2実施例を示す、第2実施例は背面
投映型のシステムであり、同図中、22は図示しないコ
ンピュータ、ビデオテープレコーダ等の映像信号を再生
する液晶パネルであり、この再生された映像信号は投映
光源21からの光によって投映レンズ24を介し2て投
映面25に背面(見る側の反対側の面)から投映される
。また、26は投映面25に偏光特性を持たせる為の偏
光板であり紙面と垂直な方向の偏光方向、を有し、23
は液晶パネル22の出射側の偏光板であり偏光板26と
同じく紙面と垂直方向の偏光特性を映像光29に付与し
、27は室内照明用の光源、28は室内照明光に偏光特
性を与える為の偏光板で紙面と平行な方向の偏光特性を
有している。
第2実施例において、投映面25に投映された再生像は
、液晶パネル22の出射側偏光板23により偏光板26
と同一の偏光特性を持たされる為、偏光板26をそのま
ま透過することが出来る。一方、室内の照明光源27の
直接光は、偏光板28により偏光板26と垂直な偏光特
性を有する如く設定されている為、偏光板26は殆ど通
過出来ない、このように投映面25上への照明による直
接光の入射がない為、投映面25上でのコントラストが
改善される。
前記第1実施例と同じ偏光板26及び28と液晶パネル
22を用い、偏光板26.28が無い場合の投映面25
上で、の室内照明用光源の直接光を液晶パネル22の明
画素の強度と同一に設定した場合、コントラストは次の
様になる。
コントラスト= (Ian+Io +IM )/ (t
。rr+I。+l5)
=(20I。et +201ott XO,25xO,
1+2I。、。
xo、25” )/ (1゜ft+
201、rf Xo、25X0゜
1+21.rr Xo、25”)
= (20+0.5+0.125
)/(1+0.5+0.12
5)412.7
第2実施例においては、照明光源27からの光は投映面
25への入射及び反射の際に1回ずつ合計2回偏光板2
6を通過するが、投映光29は投映面25に投映され出
射する際に1度偏光板26を通過するのみである。従っ
て、偏光板26による投映光強度の減少が小さいと言う
特長がある。
ところで、上記実施例では投映面に映像表示する投映光
は液晶パネルが用いられていたが1表示用デバイスとし
てはその他種々のもの(例えば電気光学結晶を用いたも
の、プラズマ表示パネルなど)が使用されつる。
[発明の効果]
以上説明した様に、本発明の構成によれば、出席者がメ
モ等を行なう為に必要な室内照明を行なっても1表示デ
バイスからの映像光により投映面上に良好なコントラス
トを持った像が得られる。By the way, this type of projection video display device is used in places such as conferences. It must be used under adequate lighting so that attendees can take notes and take notes. However, in the above-mentioned conventional example, the liquid crystal panel suitably used in the projection type image display device has a drawback that it is difficult to see when used under illumination because the intensity of the projected light is low. This will be further explained using FIG. 5. In the figure, 50 is an image of bright pixels reproduced on the liquid crystal panel on the projection surface 52, and the intensity of the light is expressed as . Also,
51 is an image of the dark pixel reproduced on the liquid crystal panel on the projection surface 52, and the intensity of the light is I. t, projection surface 52
In addition to the projected light from the liquid crystal panel, direct light (intensity 1o) from the illumination light source and indirect light (intensity ts) resulting from reflection of the light from the illumination light source within the room are incident on the top. Here, indirect light is generally 1/1 that of direct light.
The ratio of transmitted light intensity between bright pixels and dark pixels of a liquid crystal panel is generally 10:1.
to about 50:1 (here, it is assumed to be 20:1). Here, in the first case, the indoor lighting is dimmed and the dark pixel intensity is 11. Assuming that the direct light intensity I and the direct light intensity I are equal, the ratio of the brightness of the bright pixel and the dark pixel on the projection surface 52, that is, the contrast, is as follows. (■.+Io +■.-tl + I * + I a )” (2
0I-rr +I. OIゎ 1/(x, rr L / 10 Io) = (20+1+1/10)/1+l+1/10) Given 10゜In this case, +1/1 + ■. + )/(I Although it is possible to obtain a contrast of If bright pixel intensity!. and direct light intensity! are equal, then the projection surface 5
The ratio of the brightness of bright pixels and dark pixels on 2 is Contrast = (t, s + te + Im) / (
Isrr+j. +1. ) = (20I□g+20Iett+21eer) / (Istr +20I**r+2
I*rr) = 42/2341.8, the contrast is significantly lowered and the projected image is almost invisible. To solve the above problems! In order to obtain the same contrast as in the case of 1!1, the illumination light intensity remains the same as in the second case, and how many times (k) should the projection light intensity be multiplied is as follows: 10.5= (20・k ” 1eer +20 Ie
re+21stt) / (kIott
+2゜f net + 21 o'tt・)=4
20+lO+2)/(k+20+2), so it becomes =22. That is, it can be seen that the intensity of the projection light source needs to be increased by 22 times. If the intensity of the projection light source is increased by 22 times, the power consumption will also increase by 22 times, causing a serious problem such as impractical cooling of the light source. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems by providing a projection-type video display system of the type described above, while providing sufficient indoor lighting for attendees to record memos, etc. An object of the present invention is to provide a projection type video display system that can obtain an image with a high contrast. [Means for Solving the Problems] In the present invention, which achieves the above object, in a projection type image display system that directly projects an image, a first polarization characteristic is provided to the light reaching the projection surface. 1 polarizing means;
a second polarization means for giving illumination light for illuminating the surroundings a second polarization characteristic orthogonal to the first polarization characteristic;
A third polarizing means is provided for imparting a polarization characteristic parallel to the first polarization characteristic to the projection light for displaying an image on the projection surface. [Function] In the present invention having the above configuration, the direct light from the light source for indoor lighting does not reach the projection surface because it has polarization characteristics that are different from the polarization characteristics of the projection surface, while the projected light does not reach the projection surface. Since it has the same polarization characteristics as the light beam, it reaches the projection surface, and this improves the contrast on the projection surface even though the surroundings are bright. [Example 1] Figure 1 is a diagram for explaining the first example of the present invention.
In the figure, 1 is a liquid crystal panel, which reproduces video signals from a computer, video tape recorder, etc. (not shown). The projection light reproduced by the liquid crystal panel l is projected onto the projection surface 6 via the projection lens 2 by the light from the projection light source 3. In Figure 1, 7 is a light source for indoor lighting, 4 is a polarizing plate for giving the projection surface 6 horizontal polarization characteristics (indicated by arrow 5 in the figure), and 8 is a polarizing plate for indoor illumination light. Polarization characteristics of plate 4 (
11 is a polarizing plate that schematically shows the polarization characteristic of direct indoor lighting, and 13 is indirect light of indoor lighting. This figure schematically shows the polarization characteristics of . Furthermore, since the liquid crystal panel 1 has polarizing plates on both sides of the light incident side and the light output side of the projection light source 3 (see explanation in Fig. 4).
, is governed by the polarization characteristic of the polarizing plate on the exit side, which has a polarization characteristic parallel to that of the polarizing plate 4 (indicated by arrow 12), and the polarization characteristic of the projected light is as schematically shown by the symbol IO. becomes. The operation based on the above configuration will be explained. The image reproduced on the liquid crystal panel 1 is illuminated by a projection light source 3 and projected by a projection lens 2.
However, at this time, the projected light is in a polarization state parallel to the polarizing plate 4 due to the polarization characteristics shown by the arrow 12, so that most of the projected light can pass through the polarizing plate 4. On the other hand, since the direct light from the indoor illumination light source 7 is polarized by the polarizing plate 8 at right angles to the polarizing plate 4, the polarizing plate 8
When the light from the indoor illumination light source 7, which hardly passes through the room, is diffusely reflected by various objects in the room and enters the projection surface 6,
Because the indirect light no longer has specific polarization characteristics due to diffuse reflection, it can pass through the polarizing plate 4. In the first embodiment, the polarizing plates 4 and 8 have a transmittance of 90% for light in the same polarization direction as the polarizing plates, a transmittance of 1% for light in a direction perpendicular to the polarizing plates, and natural light (unpolarized light). light)
A polarizing plate with a transmittance of 25% is used, a liquid crystal spring is used in which the intensity ratio of bright pixels to dark pixels of the liquid crystal panel 1 is 20:] as in the conventional example, and furthermore, there are no polarizing plates 4 and 8. When the intensity of the direct light from the light source 7 for indoor lighting is
(The intensity of the indirect light is set to be 1/10 of the direct light as in the conventional example described above.) When the polarizing plates 4, 8, etc. are used under such setting conditions (these conditions are not special but general), the contrast on the projection surface 6 is as follows. Contrast = (1,, +I.+Is) / CI@
tt +Io +Ia) = (201,tt xo, 9+20 1*rt xQ, 25XO,t+ 2I□f Xo, 25X0.2 5)/ (I.tt xQ, 9+2 0■.tt xQ, 25xO, 1 +21att 25XO. 25) = (18+0.5+0.125)/(0.9+0.5+0°125)41・2.2 This value is considered to be sufficient as it provides more contrast than when the indoor lighting was dimmed in the conventional example. Vine. In this way, according to the IT embodiment, the contrast on the projection surface 6 can be made sufficient while making the indoor lighting sufficiently bright. Here, as mentioned above, the brightness of the indoor lighting is reduced to 25% due to the presence of the polarizing plate 8, so the intensity of the indoor lighting is reduced to 4.
Consider what happens when you double the amount. In this case, the contrast is "Contrast" (201-tt xQ, 9+80ra
texQ, 25XO, 1+ 81 oee X O-25") / (Ierr
XQ, 9+80 ratexQ, 25xO-1+8
I-r, xo, 252) = (18+2+0.5)/(Q, 9+2+0.5) The contrast is 6.0, and although the contrast is slightly lower, a sufficiently good contrast can be obtained. In actual operation, the reflected light from the projection surface 6 is further seen through the polarizing plate 4, and since the polarization direction is almost preserved in this reflection, the projected light 10 is reflected after being reflected from the projection surface 6. Nearly 90% of the light passes through the polarizing plate 4. On the other hand, the illumination light is reflected by the projection surface 6 and then attenuated by the polarizing plate 4 again. Therefore, the contrast when actually viewing the projection surface 6 is better than the above calculated value. FIG. 2 shows a second embodiment of the present invention. The second embodiment is a rear projection type system, and in the figure, 22 is a liquid crystal panel for reproducing video signals from a computer, video tape recorder, etc. (not shown). The reproduced video signal is projected by light from the projection light source 21 through the projection lens 24 onto the projection surface 25 from the back side (the surface opposite to the viewing side). Further, 26 is a polarizing plate for imparting polarization characteristics to the projection surface 25, and has a polarization direction perpendicular to the paper surface.
is a polarizing plate on the exit side of the liquid crystal panel 22, which, like the polarizing plate 26, imparts polarization characteristics perpendicular to the plane of the paper to the image light 29; 27 is a light source for indoor lighting; and 28 imparts polarization characteristics to the indoor illumination light. It is a polarizing plate for light and has polarization characteristics in the direction parallel to the paper surface. In the second embodiment, the reproduced image projected onto the projection surface 25 is transmitted to the polarizing plate 26 by the output-side polarizing plate 23 of the liquid crystal panel 22.
Since the light has the same polarization characteristics as the light, it can pass through the polarizing plate 26 as it is. On the other hand, the direct light from the indoor illumination light source 27 is set by the polarizing plate 28 so that it has polarization characteristics perpendicular to the polarizing plate 26, so it hardly passes through the polarizing plate 26. Since there is no direct light incident due to illumination, the contrast on the projection surface 25 is improved. The projection surface 25 uses the same polarizing plates 26 and 28 and the liquid crystal panel 22 as in the first embodiment, but without the polarizing plates 26 and 28.
If the direct light from the indoor lighting light source is set to have the same intensity as the bright pixels of the liquid crystal panel 22, the contrast will be as follows. Contrast = (Ian+Io +IM)/(t
. rr+I. +l5) = (20I.et +201ott XO, 25xO,
1+2I. ,. xo, 25”)/(1°ft+201, rf Xo, 25X0°1+21.rr The light from the illumination light source 27 passes through the polarizing plate 2 twice in total, once when it is incident on the projection surface 25 and once when it is reflected.
However, the projected light 29 only passes through the polarizing plate 26 once when it is projected onto the projection surface 25 and exits. Therefore, there is an advantage that the reduction in the intensity of projected light due to the polarizing plate 26 is small. By the way, in the above embodiment, a liquid crystal panel was used as the projection light for displaying images on the projection surface, but various other display devices (for example, those using electro-optic crystals, plasma display panels, etc.) may be used as display devices. It's coming. [Effects of the Invention] As explained above, according to the configuration of the present invention, even if the room is illuminated to allow attendees to take notes, the image light from one display device can provide a good image on the projection surface. An image with contrast can be obtained.
第1図は本発明の第1実施例の説明図、第2図は第2実
施例の説明図、第3図は従来例を示す図、第4図は液晶
パネルの例を示す図、第5図は従来例の問題点を説明す
る為の図である。
1.22・・・・・液晶パネル、2.24・・・・・投
映レンズ、3.21・・・・・投映光源、4.26・・
・・・偏光板(第1の偏光手段)、6.25・・・・・
投映面、7.27・・・・・室内の照明用光源、8.2
8・・・・・偏光板(第2の偏光手段)、23・・・・
・出射側偏光板(第3の偏光手段)FIG. 1 is an explanatory diagram of a first embodiment of the present invention, FIG. 2 is an explanatory diagram of a second embodiment, FIG. 3 is a diagram of a conventional example, FIG. 4 is a diagram of an example of a liquid crystal panel, and FIG. FIG. 5 is a diagram for explaining the problems of the conventional example. 1.22...Liquid crystal panel, 2.24...Projection lens, 3.21...Projection light source, 4.26...
...Polarizing plate (first polarizing means), 6.25...
Projection surface, 7.27...Light source for indoor lighting, 8.2
8...Polarizing plate (second polarizing means), 23...
・Output side polarizing plate (third polarizing means)
Claims (1)
おいて、投映面に達する光に第1の偏光特性を持たせる
為の第1の偏光手段と、周囲を照明する為の照明光に上
記第1の偏光特性と直交する第2の偏光特性を持たせる
為の第2の偏光手段と、投映面に映像を表示する投映光
に上記第1の偏光特性と平行な偏光特性を持たせる為の
第3の偏光手段が具備されている投映型映像表示システ
ム。 2、上記投映光は液晶パネルを光源からの光で照明する
ことにより作られる請求項1記載の投映型映像表示シス
テム。[Scope of Claims] 1. In a projection type image display system that projects an image on a projection surface, a first polarization means for imparting a first polarization characteristic to light reaching the projection surface, and a first polarization means for illuminating the surroundings. a second polarizing means for giving the illumination light a second polarization characteristic orthogonal to the first polarization characteristic; and a second polarization means for giving the illumination light a second polarization characteristic orthogonal to the first polarization characteristic, and a polarization parallel to the first polarization characteristic to the projection light for displaying an image on the projection surface. A projection type image display system equipped with a third polarization means for imparting characteristics. 2. The projection type video display system according to claim 1, wherein the projection light is produced by illuminating a liquid crystal panel with light from a light source.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP1226840A JPH0389316A (en) | 1989-09-01 | 1989-09-01 | Projection type video display system |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP1226840A JPH0389316A (en) | 1989-09-01 | 1989-09-01 | Projection type video display system |
Publications (1)
Publication Number | Publication Date |
---|---|
JPH0389316A true JPH0389316A (en) | 1991-04-15 |
Family
ID=16851393
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP1226840A Pending JPH0389316A (en) | 1989-09-01 | 1989-09-01 | Projection type video display system |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH0389316A (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5335022A (en) * | 1992-01-31 | 1994-08-02 | Bell Communications Research, Inc. | High-contrast front projection video display system |
EP0731603A3 (en) * | 1995-03-08 | 1997-10-01 | Seiko Epson Corp | Video projection type display device |
WO2005010577A1 (en) * | 2003-07-17 | 2005-02-03 | Nitto Denko Corporation | Liquid crystal projection system |
WO2005093512A1 (en) * | 2004-03-26 | 2005-10-06 | Matsushita Electric Industrial Co., Ltd. | Video display system |
CN110441982A (en) * | 2014-02-14 | 2019-11-12 | 大日本印刷株式会社 | Screen framework and image display system |
-
1989
- 1989-09-01 JP JP1226840A patent/JPH0389316A/en active Pending
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5335022A (en) * | 1992-01-31 | 1994-08-02 | Bell Communications Research, Inc. | High-contrast front projection video display system |
EP0731603A3 (en) * | 1995-03-08 | 1997-10-01 | Seiko Epson Corp | Video projection type display device |
US6005644A (en) * | 1995-03-08 | 1999-12-21 | Seiko Epson Corporation | Projection display employing circular polarized light for reflection reduction |
WO2005010577A1 (en) * | 2003-07-17 | 2005-02-03 | Nitto Denko Corporation | Liquid crystal projection system |
US7234817B2 (en) | 2003-07-17 | 2007-06-26 | Nitto Denko Corporation | Liquid crystal projection system |
WO2005093512A1 (en) * | 2004-03-26 | 2005-10-06 | Matsushita Electric Industrial Co., Ltd. | Video display system |
CN110441982A (en) * | 2014-02-14 | 2019-11-12 | 大日本印刷株式会社 | Screen framework and image display system |
CN110441982B (en) * | 2014-02-14 | 2021-10-15 | 大日本印刷株式会社 | Screen housing and image display system |
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