JPH04323979A - Distortion correction circuit for liquid crystal projector - Google Patents
Distortion correction circuit for liquid crystal projectorInfo
- Publication number
- JPH04323979A JPH04323979A JP3092207A JP9220791A JPH04323979A JP H04323979 A JPH04323979 A JP H04323979A JP 3092207 A JP3092207 A JP 3092207A JP 9220791 A JP9220791 A JP 9220791A JP H04323979 A JPH04323979 A JP H04323979A
- Authority
- JP
- Japan
- Prior art keywords
- liquid crystal
- display period
- screen
- picture
- crystal projector
- 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.)
- Granted
Links
- 239000004973 liquid crystal related substance Substances 0.000 title claims abstract description 19
- 238000005070 sampling Methods 0.000 claims description 4
- 230000006835 compression Effects 0.000 description 7
- 238000007906 compression Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 5
- 238000003780 insertion Methods 0.000 description 4
- 230000037431 insertion Effects 0.000 description 4
- 230000007423 decrease Effects 0.000 description 1
Landscapes
- Projection Apparatus (AREA)
- Liquid Crystal Display Device Control (AREA)
- Transforming Electric Information Into Light Information (AREA)
Abstract
Description
【０００１】0001
【産業上の利用分野】本発明は前面投射型の液晶プロジ
ェクタにおける台形歪みを補正する歪み補正回路に関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distortion correction circuit for correcting keystone distortion in a front projection type liquid crystal projector.
【０００２】0002
【従来の技術】従来、特開平１−１２０１９２号公報に
示されるような前面投射型の液晶プロジェクタは、図４
に示す如くプロジェクタ本体１をスクリーン２に対して
傾斜して配置した場合、スクリーン２に対する投射角度
が直角とならず、上下で画面横方向の長さが異なる台形
歪みと呼ばれる歪みが発生する。2. Description of the Related Art Conventionally, a front projection type liquid crystal projector as shown in Japanese Unexamined Patent Publication No. 1-120192 is shown in FIG.
When the projector main body 1 is arranged at an angle with respect to the screen 2 as shown in FIG. 2, the projection angle to the screen 2 is not perpendicular, and a distortion called trapezoidal distortion occurs in which the horizontal length of the screen is different between the upper and lower sides.
【０００３】従来の液晶プロジェクタはこの台形歪みに
対しては何ら対策が施されていなかった。Conventional liquid crystal projectors have not taken any measures against this trapezoidal distortion.
【０００４】0004
【発明が解決しようとする課題】本発明は上述の点に鑑
み為されたものであり、台形歪みをなくした液晶プロジ
ェクタを提供するものである。SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is an object of the present invention to provide a liquid crystal projector that eliminates trapezoidal distortion.
【０００５】[0005]
【課題を解決するための手段】本発明は、所定周波数の
クロックにより動作するシフトレジスタと、このシフト
レジスタ出力をサンプリングパルスとして映像信号をサ
ンプリングしホールドするサンプルホールド回路と、こ
のサンプルホールド回路出力により駆動される液晶パネ
ルとを少なくとも備える液晶プロジェクタにおいて、画
面の垂直位置に応じて映像信号の有効表示期間内と有効
表示期間外とでのクロック数の比を順次変化させる手段
を設けてなることを特徴とする液晶プロジェクタの歪み
補正回路である。[Means for Solving the Problems] The present invention provides a shift register operated by a clock of a predetermined frequency, a sample hold circuit that samples and holds a video signal using the output of the shift register as a sampling pulse, and an output of the sample hold circuit. A liquid crystal projector comprising at least a driven liquid crystal panel is provided with means for sequentially changing the ratio of the number of clocks between a video signal within an effective display period and outside the effective display period according to the vertical position of the screen. This is a characteristic distortion correction circuit for liquid crystal projectors.
【０００６】[0006]
【作用】上述の手段により、画面の垂直位置に応じて映
像信号の有効表示期間内と有効表示期間外とでのクロッ
ク数の比が順次変化し水平方向における画像の圧縮率が
垂直位置に応じて変化するよう作用する。[Operation] By means of the above-mentioned means, the ratio of the number of clocks within the effective display period of the video signal and outside the effective display period changes sequentially according to the vertical position of the screen, and the compression ratio of the image in the horizontal direction changes according to the vertical position. It acts so that it changes.
【０００７】[0007]
【実施例】まず、本発明の原理を説明する。図４の如く
プロジェクタ本体１をスクリーン２より下に配置した場
合、スクリーン２上に映出される画像は上辺が下辺より
長い台形となる。そして、これを補正するには予め液晶
パネルに印加される画像信号を細工し、このパネル上の
画像が前記とは逆の台形となるようにする。即ち、液晶
パネルの画素数が水平４８０画素、２４０ラインとする
と、図１（イ）の如く補正を行わない場合は映像信号の
有効表示期間を４８０画素で表示するが、同図（ロ）の
如く補正を行う場合は、映像信号の有効表示期間を圧縮
して４８０−２ｍ画素で表示し前後の各ｍ画素には付加
ブランキングを表示する。このようにすれば、スクリー
ン上で台形歪みが補正され方形の画像が得られる。尚、
ｍは歪みに応じた補正量である。[Example] First, the principle of the present invention will be explained. When the projector main body 1 is arranged below the screen 2 as shown in FIG. 4, the image projected on the screen 2 has a trapezoidal shape in which the upper side is longer than the lower side. To correct this, the image signal applied to the liquid crystal panel is modified in advance so that the image on this panel becomes a trapezoid, which is the opposite of the above. In other words, if the number of pixels of the liquid crystal panel is 480 horizontal pixels and 240 lines, the effective display period of the video signal will be displayed as 480 pixels if no correction is performed as shown in Figure 1 (B), but as shown in Figure 1 (B). When performing such correction, the effective display period of the video signal is compressed and displayed with 480-2 m pixels, and additional blanking is displayed on each of the m pixels before and after the video signal. In this way, trapezoidal distortion is corrected on the screen and a rectangular image is obtained. still,
m is a correction amount according to distortion.
【０００８】次に、図面に従い本発明の一実施例を説明
する。Next, one embodiment of the present invention will be described with reference to the drawings.
【０００９】図３は本実施例装置のブロック図であり、
３は４８０画素×２４０行の液晶パネル、４はＸドライ
バを構成するシフトレジスタ、５、６はそれぞれＹドラ
イバを構成するシフトレジスタ及びサンプルホールド回
路であり、これらは従来より公知の駆動回路である。FIG. 3 is a block diagram of the device of this embodiment.
3 is a liquid crystal panel with 480 pixels x 240 lines; 4 is a shift register that constitutes an X driver; and 5 and 6 are shift registers and sample hold circuits that constitute Y drivers, respectively; these are conventionally known drive circuits. .
【００１０】また、７は垂直同期信号でリセットされ水
平同期信号をカウントするライン数カウンタ、８は操作
者が画面を見ながら操作する＋−の補正キー（図示省略
）からの指示を受け、最大補正ラインの補正量をｍとし
て出力する補正量指示手段、９はこのライン数カウンタ
７からの垂直位置を示す信号及び補正量指示手段９から
の補正量ｍにより水平方向の圧縮率を決定する水平圧縮
率決定手段、１０は高速クロックを１／２分周して１ラ
インにつき６００の低速クロックを発生する分周手段、
１１は水平同期信号によりリセットされ前記分周したク
ロックをカウントする画素数カウンタ、１２は前記水平
圧縮率決定手段からの出力及び前記画素数カウンタ出力
により有効表示期間のクロックを間引くため所定クロッ
ク毎にマスクパルスを発生するマスクパルス発生手段、
１３は有効表示期間に間引くクロックと同数のクロック
を有効表示期間の前後に挿入するため、前記水平圧縮率
決定手段出力と画素数カウンタ出力により高速クロック
挿入位置を指定する高速クロック挿入位置指定手段、１
４は前記低速クロックと前記マスクパルスを加算する加
算手段、１５は前記高速クロック挿入位置指定手段出力
により制御され、前記高速クロックと前記加算手段出力
とを切り替えてシフトレジスタのクロック端子に印加す
るスイッチである。Further, 7 is a line number counter that is reset by the vertical synchronization signal and counts the horizontal synchronization signal, and 8 is a line number counter that is reset by the vertical synchronization signal and counts the horizontal synchronization signal. Correction amount indicating means 9 outputs the correction amount of the correction line as m, and 9 is a horizontal means 9 for determining the compression ratio in the horizontal direction based on the signal indicating the vertical position from the line number counter 7 and the correction amount m from the correction amount indicating means 9. compression ratio determining means; 10 is a frequency dividing means for dividing the high speed clock by 1/2 to generate 600 low speed clocks per line;
11 is a pixel number counter that is reset by the horizontal synchronization signal and counts the frequency-divided clock; 12 is a pixel number counter that is reset by the horizontal synchronization signal and counts the frequency-divided clock; 12 is a pixel number counter that thins out the clocks in the effective display period by the output from the horizontal compression rate determining means and the output of the pixel number counter at every predetermined clock interval; mask pulse generation means for generating mask pulses;
13 is a high-speed clock insertion position specifying means for specifying a high-speed clock insertion position based on the output of the horizontal compression ratio determining means and the output of the pixel number counter in order to insert the same number of clocks as the clocks to be thinned out in the effective display period before and after the effective display period; 1
4 is an addition means for adding the low-speed clock and the mask pulse; 15 is a switch controlled by the output of the high-speed clock insertion position specifying means, and for switching between the high-speed clock and the output of the addition means and applying it to the clock terminal of the shift register; It is.
【００１１】次に、図１（ロ）の様に補正する場合を例
にとって、図３を参照しつつ動作を説明する。Next, the operation will be explained with reference to FIG. 3, taking as an example the case of correction as shown in FIG. 1(b).
【００１２】まず、ライン数カウンタ７は駆動ラインを
示す信号を水平圧縮率決定手段８に出力する。水平圧縮
率決定手段８では補正量指示手段９からの最大補正量ｍ
により各ラインの補正量を決定する。例えば、ｍが４０
であれば１ライン目は補正量は４０、１２０ライン目は
２０、２４０ライン目は０となる。そして、この出力に
基づいてマスクパルス発生手段１２では水平位置上でど
のタイミングでクロックを間引くかを決定し、２クロッ
ク分のパルス幅をもつマスクパルスを発生する。そして
、低速クロックはこのマスクパルスにより加算手段１５
でマスクされスイッチ１４へ供給される。First, the line number counter 7 outputs a signal indicating the driving line to the horizontal compression ratio determining means 8. The horizontal compression ratio determination means 8 determines the maximum correction amount m from the correction amount instruction means 9.
Determine the amount of correction for each line. For example, m is 40
In this case, the correction amount will be 40 for the 1st line, 20 for the 120th line, and 0 for the 240th line. Then, based on this output, the mask pulse generating means 12 determines at what timing on the horizontal position the clocks should be thinned out, and generates a mask pulse having a pulse width of two clocks. Then, the low-speed clock is output to the adding means 15 by this mask pulse.
The signal is masked and supplied to the switch 14.
【００１３】一方、間引いたクロックと同数のクロック
を２分してそれぞれ有効表示期間の前後に挿入するため
、スイッチ１４により所定期間低速クロックを高速クロ
ックに切り替える。このスイッチは高速クロック挿入位
置指定手段１３出力により制御される。On the other hand, in order to divide the same number of clocks into two and insert them before and after the effective display period, the switch 14 switches the low-speed clock to the high-speed clock for a predetermined period. This switch is controlled by the output of the high speed clock insertion position specifying means 13.
【００１４】この様にして作成されたクロックは前記シ
フトレジスタ５に供給されサンプリングパルスとされた
後サンプルホールド回路６に供給される。The clock generated in this manner is supplied to the shift register 5, converted into a sampling pulse, and then supplied to a sample and hold circuit 6.
【００１５】また、シフトレジスタ５のスタートパルス
は図３（イ）の映像信号の水平同期信号から低速クロッ
クを６０クロックカウントした時、発生するパルスを使
用している。Further, the start pulse of the shift register 5 uses a pulse generated when 60 low-speed clocks are counted from the horizontal synchronizing signal of the video signal shown in FIG. 3(A).
【００１６】従って、図３（ロ）のごとく１ライン目は
スタートパルスが正常時より早く現れサンプリングが早
く行われるため最初はブランキング信号が液晶パネルに
供給され、また有効表示期間のクロック数が少ないため
映像信号の供給は早く終わる。結果として画像は圧縮し
て表示される。そして、この割合は下のラインに進につ
れて少なくなり２４０ラインでは（ニ）の如くクロック
には何ら細工されず画像は圧縮されない。Therefore, as shown in FIG. 3(b), on the first line, the start pulse appears earlier than in the normal state and sampling is performed earlier, so a blanking signal is initially supplied to the liquid crystal panel, and the number of clocks during the effective display period is Since the number of video signals is small, the supply of video signals ends quickly. As a result, the image is displayed compressed. This ratio decreases as the line progresses to the bottom, and at line 240, as shown in (d), the clock is not manipulated at all and the image is not compressed.
【００１７】尚、プロジェクタ本体をスクリーンより上
方に配置したときは上下で逆の補正とするよう動作する
。[0017] When the projector body is placed above the screen, it operates so that the vertical correction is reversed.
【００１８】[0018]
【発明の効果】上述の如く本発明によれば液晶プロジェ
クタの台形歪みを簡単な回路で補正することができる。As described above, according to the present invention, trapezoidal distortion of a liquid crystal projector can be corrected with a simple circuit.
【図１】本発明の原理を示す図。FIG. 1 is a diagram showing the principle of the present invention.
【図２】本発明の一実施例における歪み補正装置のブロ
ック図。FIG. 2 is a block diagram of a distortion correction device in an embodiment of the present invention.
【図３】図２の要部波形図。FIG. 3 is a waveform diagram of main parts in FIG. 2;
【図４】台形歪みの説明図。FIG. 4 is an explanatory diagram of trapezoidal distortion.
１ 液晶プロジェクタ本体２
スクリーン
３ 液晶パネル
４、５ シフトレジスタ
６ サンプルホールド回路８
補正量指示手段1 LCD projector body 2
Screen 3 LCD panel 4, 5 Shift register 6 Sample hold circuit 8
Correction amount indicating means
Claims (1)
シフトレジスタと、このシフトレジスタ出力をサンプリ
ングパルスとして映像信号をサンプリングしホールドす
るサンプルホールド回路と、このサンプルホールド回路
出力により駆動される液晶パネルとを少なくとも備える
液晶プロジェクタにおいて、画面の垂直位置に応じて映
像信号の有効表示期間内と有効表示期間外とでのクロッ
ク数の比を順次変化させる手段を設けてなることを特徴
とする液晶プロジェクタの歪み補正回路。1. At least a shift register operated by a clock of a predetermined frequency, a sample hold circuit that samples and holds a video signal using the output of the shift register as a sampling pulse, and a liquid crystal panel driven by the output of the sample hold circuit. Distortion correction for a liquid crystal projector, characterized in that the liquid crystal projector is provided with means for sequentially changing the ratio of the number of clocks between the effective display period and the outside of the effective display period of a video signal according to the vertical position of the screen. circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3092207A JP2925777B2 (en) | 1991-04-23 | 1991-04-23 | LCD projector distortion correction circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3092207A JP2925777B2 (en) | 1991-04-23 | 1991-04-23 | LCD projector distortion correction circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04323979A true JPH04323979A (en) | 1992-11-13 |
| JP2925777B2 JP2925777B2 (en) | 1999-07-28 |
Family
ID=14048001
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3092207A Expired - Fee Related JP2925777B2 (en) | 1991-04-23 | 1991-04-23 | LCD projector distortion correction circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2925777B2 (en) |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5471295A (en) * | 1993-01-19 | 1995-11-28 | Matsushita Electric Industrial Co., Ltd. | Angle measuring method and apparatus using projected graphic |
| EP0783132A1 (en) * | 1995-11-29 | 1997-07-09 | Daewoo Electronics Co., Ltd | Apparatus for detecting angle of inclination of an image projector with respect to its support plane |
| EP0773678A3 (en) * | 1995-11-13 | 1998-03-04 | Daewoo Electronics Co., Ltd | Method for pre-compensating an asymmetrical picture in a projection system for displaying a picture |
| EP0773679A3 (en) * | 1995-11-13 | 1998-03-11 | Daewoo Electronics Co., Ltd | Method for pre-compensating an asymmetrical picture in a projection system for displaying a picture |
| EP0756425A3 (en) * | 1995-07-25 | 1998-10-14 | Daewoo Electronics Co., Ltd | Method and apparatus for correcting trapezoidal image distortion in a display projection system by modifying image signals |
| DE19737374A1 (en) * | 1997-08-27 | 1999-03-04 | Ldt Gmbh & Co | Method for compensating geometric image errors in video images and a device for carrying out the method |
| WO1999043155A1 (en) * | 1998-02-18 | 1999-08-26 | Seiko Epson Corporation | Image processing device and image processing method |
| KR20020000940A (en) * | 2000-06-22 | 2002-01-09 | 구자홍 | Apparatus and method for correcting keystone |
| US6609797B2 (en) | 1999-01-29 | 2003-08-26 | Ricoh Co., Ltd | Projector with adjustably positioned image plate |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0276485A (en) * | 1988-09-13 | 1990-03-15 | Pioneer Electron Corp | Video signal processing circuit in projection tv |
| JPH0380780A (en) * | 1989-08-24 | 1991-04-05 | Victor Co Of Japan Ltd | Trapezoidal distortion correction circuit for image projector using liquid crystal light valve |
| JPH0380682A (en) * | 1989-08-23 | 1991-04-05 | Victor Co Of Japan Ltd | Trapezoidal distortion correcting circuit for image projector using liquid crystal light valve |
-
1991
- 1991-04-23 JP JP3092207A patent/JP2925777B2/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0276485A (en) * | 1988-09-13 | 1990-03-15 | Pioneer Electron Corp | Video signal processing circuit in projection tv |
| JPH0380682A (en) * | 1989-08-23 | 1991-04-05 | Victor Co Of Japan Ltd | Trapezoidal distortion correcting circuit for image projector using liquid crystal light valve |
| JPH0380780A (en) * | 1989-08-24 | 1991-04-05 | Victor Co Of Japan Ltd | Trapezoidal distortion correction circuit for image projector using liquid crystal light valve |
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5471295A (en) * | 1993-01-19 | 1995-11-28 | Matsushita Electric Industrial Co., Ltd. | Angle measuring method and apparatus using projected graphic |
| EP0756425A3 (en) * | 1995-07-25 | 1998-10-14 | Daewoo Electronics Co., Ltd | Method and apparatus for correcting trapezoidal image distortion in a display projection system by modifying image signals |
| EP0773678A3 (en) * | 1995-11-13 | 1998-03-04 | Daewoo Electronics Co., Ltd | Method for pre-compensating an asymmetrical picture in a projection system for displaying a picture |
| EP0773679A3 (en) * | 1995-11-13 | 1998-03-11 | Daewoo Electronics Co., Ltd | Method for pre-compensating an asymmetrical picture in a projection system for displaying a picture |
| EP0783132A1 (en) * | 1995-11-29 | 1997-07-09 | Daewoo Electronics Co., Ltd | Apparatus for detecting angle of inclination of an image projector with respect to its support plane |
| DE19737374A1 (en) * | 1997-08-27 | 1999-03-04 | Ldt Gmbh & Co | Method for compensating geometric image errors in video images and a device for carrying out the method |
| DE19737374C2 (en) * | 1997-08-27 | 1999-09-02 | Ldt Gmbh & Co | Method for compensating geometric image errors in video images and a projector for carrying out the method |
| US6590606B1 (en) | 1997-08-27 | 2003-07-08 | Ldt Gmbh & Co. Laser-Display-Technology Kg | Method for the compensating of geometric images and an arrangement for carrying out the method |
| WO1999043155A1 (en) * | 1998-02-18 | 1999-08-26 | Seiko Epson Corporation | Image processing device and image processing method |
| US6450647B1 (en) | 1998-02-18 | 2002-09-17 | Seiko Epson Corporation | Image processing device and image processing method |
| US6609797B2 (en) | 1999-01-29 | 2003-08-26 | Ricoh Co., Ltd | Projector with adjustably positioned image plate |
| KR20020000940A (en) * | 2000-06-22 | 2002-01-09 | 구자홍 | Apparatus and method for correcting keystone |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2925777B2 (en) | 1999-07-28 |
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