JP2004347911A - Projector and automatic focusing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct the trapezoidal distortion of an image on a screen by using a passive range-finding device having a pair of line sensors and also to perform the focusing of the image on the screen by using the pair of line sensors without using a light emitting element in a projector. <P>SOLUTION: The projector (2) includes a projection lens optical system (8) projecting the image to the screen (1), an angle detector including a pair of line sensors (31c and 31d) for correcting the trapezoidal distortion of the image projected to the screen by the optical system (8), and an automatic focus detector (20) receiving the image projected to the screen by using a pair of line sensors so as to detect the focusing position of the image projected thereto while moving the focal position of the optical system (8), measuring a spot where the high frequency component of an image signal becomes maximum, and adjusting the focal position of the optical system (8) to the spot where the high frequency component becomes maximum. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

ここで、Ｌ（）：基準部３１ｃ側センサーデータ
Ｓａ ：基準部３１ｃ側受光素子最小Ｎｏ．
Ｗｎ ：部分群の受光素子数
ｔ ；整数（一般的に１〜４）
ノイズの影響を解除するためには、差分の絶対値が所定値（ノイズキャンセルレベル）以下の場合は、総和に加えない。
なお、ラインセンサ３１ｃの一列に配列された受光素子（画素）にはそれぞれ一連の通し番号（画素番号）がふってある。
【００７９】
次ぎに図２０を参照して、別の方法によるパッシブ型ライン測距装置３を用いて傾斜角度θ１の計算方法を説明する。図２０に示すように、ライン型パッシブ測距装置３の基線長ｋ方向（プロジェクタ２の水平方向）に対するスクリーン１の傾斜角度をθ１とし、図１２で説明した方法により、ラインセンサ３１ｃの測距演算領域３１ｃ７の測距方向に沿って測距演算して算出されたスクリーン１までの距離がＬ１、測距演算領域３１ｃ３の測距方向に沿って測距演算して算出されたスクリーン１までの距離がＬ２とする。予め知られている測距演算領域３１ｃ３の測距方向と基線長方向に垂直な方向とがなす角度をβとし、同じく予め知られている測距演算領域３１ｃ７の測距方向と基線長方向に垂直な方向とがなす角度をγとする。傾斜角度θ１は、次式で計算される。
【００８０】
θ１＝ａｒｃｔａｎ（Ｌ２ｃｏｓβ−Ｌ１ｃｏｓγ）／（Ｌ１ｓｉｎγ＋Ｌ２ｓｉｎβ）
【００８１】
このようにして、図１０に示す制御回路５はスクリーン１の傾斜角度を計算して、得られた傾斜角度に基づいてスクリーン１上の画像の台形歪みを補正する。上記において図５のステップ５８に関連して説明したように、台形歪みを補正した後、測距装置３によりプロジェクタ２からスクリーン１までの距離を測定して、投影レンズ光学系８の焦点調節を再度行なう。具体的には、例えば、制御回路５が測距装置で測定したスクリーン１までの距離に対応する投影レンズ光学系８の焦点位置に基づいた信号を光学系駆動部２３に出力し、光学系駆動部２３が上記焦点位置まで投影レンズ光学系８を駆動することによって焦点調節を行なう。これは、台形歪み補正後の焦点の変動を補正し、また、比較的大型スクリーンの場合にはスクリーンの特定箇所、例えば、中央位置、の画像の焦点が特に合うように投影レンズ光学系の焦点を再調節するためである。この再調節は投影レンズ光学系８の図５のステップ５６の山登り式ＡＦによる合焦位置からの移動が少ない微調整ですみ、電力消費を抑えることができる。
【００８２】
なお、図５のステップ５６の山登り式ＡＦの代わりに、測距装置３の一対のラインセンサを使用した位相差測定による測距操作を電源投入時にして、その測距データに基づいて合焦調節をすれば、焦点検出装置２０が不要となることも考えられる。しかし、ステップ５５の電源投入時等の初期時にはスクリーン上の画像のピントが合っていないことが考えられ、スクリーン上の画像のコントラストが低い。従って、測距装置３の一対のラインセンサが検出する位相差の精度が低くく、測距結果の精度も低くくなり、測距装置３の一対のラインセンサでは合焦調節が正確にできない場合が発生すると考えられる。そして、スクリーン上の画像のコントラストが低くいとその後の角度検出の精度も低くなり、ステップ５７の台形歪み補正も正確にできなくなる可能性が高い。よって、図５のステップ５６の合焦調節は投影レンズ光学系８を動かしてスクリーン上に投影される画像の高周波成分又はコントラストデータを検出する図４及び図６に示すような山登り方式ＡＦを行なうのが好ましい。
【００８３】
【発明の効果】
以上説明したように、請求項１に記載された本発明のプロジェクタによれば、別途に発光素子を必要とせず、しかも角度検出用の一対のラインセンサを使用してスクリーン上に投影された画像の台形歪みの補正と自動合焦（オートフォーカス）の両方ができる。
【００８４】
請求項２に記載された本発明のプロジェクタによれば、一対のラインセンサの取り付け誤差や一対のラインセンサに画像を結像するレンズ特性による誤差を吸収でき、正確に合焦位置を求めて焦点調節ができ、信頼性の高いオートフォーカスが可能となる。
【００８５】
請求項３に記載された本発明のプロジェクタによれば、投影レンズ光学系を駆動する光学系駆動部が移動誤差等により１回の操作で正確に画像信号が最大となる所に投影レンズ光学系を戻すことができなくとも、画像信号が最大となる付近で所定間隔だけ両方向に投影レンズ光学系を移動して画像信号が最大となる所を再度測定することで、正確に合焦位置に調節することができる。
【００８６】
請求項４に記載された本発明の方法によれば、最初に投影レンズ光学系のスクリーン上に投影する画像の合焦位置を調節しているため、台形歪みを補正する際に使用する画像もスクリーン上に焦点が合って投影される。このため、一対のラインセンサが受光した画像はコントラストが高く、従って、高い位相差を得ることができる。この結果、比較的に高精度にプロジェクタからスクリーン上に投影された画像の複数箇所までの距離を測定することができ、スクリーンの相対的な傾斜角度を比較的高精度に求めることができ、よって高精度で台形歪みを補正することができる。さらに、台形歪み補正による焦点のずれを台形歪み補正後に一対のラインセンサによる測距操作により修正できる。
【図面の簡単な説明】
【図１】本発明の１つの実施の形態によるプロジェクタの構成を示す概略ブロック図。
【図２】図１に示したプロジェクタの概略正面図。
【図３】本発明の１つの実施の形態による自動焦点検出装置の演算部の機能ブロック図。
【図４】本発明の１つの実施の形態による自動焦点調節方法を説明するためプロジェクタの投影レンズ光学系の焦点位置を横軸に示し、その投影レンズ光学系によりスクリーン上に投影された画像の受光信号に含まれる高周波成分（又はコントラストデータ）を縦軸に示したグラフ。
【図５】本発明の１つの実施の形態によるプロジェクタの画像調節方法を示すフローチャート。
【図６】本発明の１つの実施の形態による自動焦点調節方法を示すフローチャート。
【図７】本発明の別の実施の形態による自動焦点調節方法を示すフローチャート。
【図８】図７の実施の形態による自動焦点調節方法の詳細を示すフローチャート。
【図９】図７の実施の形態による自動焦点調節方法の詳細を示すフローチャート。
【図１０】本発明の１つの実施の形態による角度検出器の機能ブロック図。
【図１１】本発明の１つの実施の形態による角度検出器に含まれる測距装置の測距操作を説明する図。
【図１２】本発明の１つの実施の形態による角度検出器に含まれる測距装置の測距操作を説明する別の図。
【図１３】本発明の１つの実施の形態による角度検出器に含まれる測距装置の一対のラインセンサの概略を示すブロック図。
【図１４】本発明の１つの実施の形態による角度検出器に含まれる測距装置による複数位置の距離測定を説明する図。
【図１５】本発明の１つの実施の形態による角度検出器に含まれる測距装置による角度検出方法を説明する図。
【図１６】本発明の１つの実施の形態による角度検出器に含まれる測距装置による角度検出方法を説明する図。
【図１７】本発明の１つの実施の形態による角度検出器に含まれる測距装置による角度検出方法を説明する図。
【図１８】本発明の１つの実施の形態による角度検出器に含まれる測距装置による角度検出方法を説明する図。
【図１９】本発明の１つの実施の形態による角度検出器に含まれる測距装置の測距演算領域のコントラスト重心位置を求める方法を説明する図。
【図２０】本発明の１つの実施の形態による角度検出器に含まれる測距装置による角度検出方法を説明する図。
【図２１】本発明の別の実施の形態による自動焦点調節方法を説明するためプロジェクタの投影レンズ光学系の焦点位置を横軸に示し、その投影レンズ光学系によりスクリーン上に投影された画像の受光信号に含まれる高周波成分（又はコントラストデータ）を縦軸に示したグラフ。
【符号の説明】
１ スクリーン
２ プロジェクタ
３ 測距装置
４ 測距装置
５ 制御回路
８ 投影レンズ光学系
２０ 自動焦点検出装置
２２ 演算部
２３ 光学系駆動部
３１ 撮像部
３１ａ レンズ
３１ｂ レンズ
３１ｃ ラインセンサ
３１ｄ ラインセンサ
３２ 演算部
ｋ 基線長
θ１ 水平面内でスクリーン１が基線長ｋ方向となす傾斜角度[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides an image signal obtained by receiving an image on a screen with the pair of line sensors while correcting the trapezoidal distortion of the image and moving the projection lens optical system by providing an angle detection device having a pair of line sensors. The present invention relates to a projector provided with an automatic focusing device that adjusts a focusing position by measuring the focus position and a method of automatically focusing an image projected on a screen.
[0002]
[Prior art]
Conventionally, in a projector such as a liquid crystal projector that projects an image on a screen using a projection lens optical system, it is necessary to automatically correct trapezoidal distortion of an image projected on the screen and perform focusing. It is desired to enhance the convenience of the projector.
[0003]
Patent Document 1 discloses a liquid crystal projector that automatically focuses an image projected on a screen using an active distance measuring device including a light emitting element.
Patent Literature 2 discloses a liquid crystal projector that calculates a relative inclination angle of a screen using an active distance measuring device including a light emitting element and automatically corrects trapezoidal distortion of an image projected on the screen. It has been disclosed.
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. H11-264963 [Patent Document 2]
Japanese Patent Application Laid-Open No. 2000-122617
[Problems to be solved by the invention]
However, in the conventional projectors described in Patent Literatures 1 and 2, the distance to the screen is measured by an active distance measurement sensor including a light emitting element to obtain focal length information or to obtain information on the relative distance to the screen. In order to determine the tilt angle, conventional projectors require separate light-emitting elements for distance measurement separately from those used for image projection, which increases the size of the structure and also requires power to emit light from the light-emitting elements for distance measurement. There is a problem. Further, in the conventional projectors described in Patent Documents 1 and 2, since an active distance measurement sensor including a light emitting element is used, light of the light emitting element does not reach a screen on which an image of the projector is projected, or light is emitted even if it reaches the screen. If the light from the element is weak, there is a problem that the distance measurement accuracy is reduced, and accurate focusing and trapezoidal distortion cannot be corrected.
[0006]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a projector and an automatic focus adjustment method which can correct trapezoidal distortion of an image projected on a screen and accurately and automatically adjust focus by solving the above-mentioned conventional problems. .
[0007]
[Means for Solving the Problems]
According to the first aspect of the present invention, a projection lens optical system for projecting an image on a screen, and a pair of trapezoidal distortions for correcting an image projected on the screen by the projection lens optical system. An angle detection device including a line sensor, and measuring the position where the image signal obtained by receiving the projected image by the pair of line sensors while moving the focal position of the projection lens optical system is maximized. There is provided a projector including an automatic focus detection device that adjusts a focal position of a lens optical system to the maximum position.
[0008]
According to the configuration of the first aspect, the distance to a plurality of images on the screen is measured by receiving the image projected on the screen by the angle detection device having the pair of line sensors and obtaining the phase difference. To calculate the relative tilt angle of the screen plane. With this angle detection device, trapezoidal distortion of an image projected on a screen can be corrected without requiring a separate light emitting element. Further, the projector projects the image projected onto the screen while moving the focal position of the projection lens optical system with a pair of line sensors of the angle detection device, and measures the image signal obtained. Then, the focal point of the projection lens optical system is adjusted using the focus position as the focus position. This focuses on the point that when the image projected on the screen is in focus, the resolution of the image is highest, and since the brightness of fine pixels is clearly displayed, the image signal is also highest. According to the present invention, both correction of trapezoidal distortion of an image projected on a screen using a pair of line sensors for angle detection and automatic focusing (autofocus) do not require a separate light emitting element. Can be.
[0009]
According to the second aspect of the present invention, there is provided the projector according to the first aspect, wherein the automatic focus detection device measures an average value of the image signals respectively received by the pair of line sensors.
[0010]
According to the configuration of the second aspect, in order to measure the average value of the image signals received by the pair of line sensors and measure the maximum value thereof, the mounting error of the pair of line sensors and the pair of line sensors are measured. An error due to the characteristics of a lens that forms an image on a sensor can be absorbed, the focus can be adjusted by accurately determining the focus position, and highly reliable autofocus can be performed.
[0011]
According to the third aspect of the present invention, the automatic focus detection device adjusts the focus position of the projection lens optical system to a position where the image signal is maximum, and then performs the projection for a predetermined interval from the position. While moving the optical lens system in the direction of the farthest focus position and the direction of the closest focus position, the position where the image signal obtained by receiving the image projected on the screen is maximized is measured again and the focus position is adjusted again. A projector according to claim 1 or 2 is provided.
[0012]
According to this configuration, after moving the entire range to detect a position where the image signal is maximum and adjusting the projection lens optical system to the position where the image signal is maximum, the projection lens optical system is moved by a predetermined interval. The focal point of the projection lens optical system is readjusted by moving again in the direction of the farthest focus position and the direction of the closest focus position to measure again the position where the image signal becomes maximum. As a result, even if the optical system driving unit that drives the projection lens optical system by the first operation cannot accurately adjust the projection lens optical system to a position where the image signal is accurately maximized due to a movement error or the like, it is possible to accurately adjust the projection lens optical system. The focus position can be adjusted.
[0013]
According to the present invention as set forth in claim 4, there is provided a method of adjusting an image projected on a screen by a projection lens optical system, wherein the image on the screen is moved while moving a focal position of the projection lens optical system. Projecting, the step of measuring the place where the image signal obtained by receiving the projected image by a pair of line sensors is maximum, and the focal position of the projection lens optical system at the place where the maximum is obtained Adjusting, and measuring the distance to the image projected on the screen using the pair of line sensors after the adjusting step, calculating the relative tilt angle of the screen, and obtaining a trapezoid of the image. After the step of correcting the distortion and the step of correcting the trapezoidal distortion, up to the image projected on the screen using the pair of line sensors. Image adjustment method comprising the step of adjusting the focal position of the projection lens optical system again the distance measured is provided.
[0014]
According to the configuration of the fourth aspect, first, the in-focus position of the image projected on the screen by the automatic focus detection device is obtained. While moving the projection lens system, a pair of line sensors is used to measure the position where the received image signal is maximum, and the position of the projection lens system is adjusted to focus on that position. When the in-focus position is detected by the automatic focus detection device, the image projected from the projector onto the screen may have a repetitive pattern if appropriate for focusing. Next, trapezoidal distortion of the image projected on the screen is corrected using a pair of line sensors. At this time, an image that does not include a repetitive pattern is projected. This is because an image including a repetitive pattern is not suitable for measuring the phase difference because the distance from the projector to a plurality of locations of the image projected on the screen is measured using the phase difference between the images received by the pair of line sensors. is there. Since the projection lens optical system adjusts the focus of the image projected on the screen, the image used for correcting the trapezoidal distortion can be projected on the screen in focus. Therefore, the images received by the pair of line sensors have high contrast, and a high phase difference can be obtained. As a result, the distance from the projector to a plurality of locations of the image projected on the screen can be measured with relatively high accuracy, and therefore, the relative tilt angle of the screen can be obtained with relatively high accuracy. Therefore, the trapezoidal distortion can be corrected with high accuracy. After correcting the trapezoidal distortion, the focus of the projection lens optical system is adjusted again. This is because the focus may be shifted when correcting the trapezoidal distortion. For this reason, the distance from the projector to a plurality of locations of the image projected on the screen is measured by a pair of line sensors, and the focus fluctuation after the trapezoidal distortion correction is corrected based on the distance measurement result. In the case of a relatively large screen, the focus of the projection lens optical system may be readjusted so that the image is particularly focused on a specific portion of the screen, for example, the center position. This focus re-adjustment requires only fine adjustment from the initial focus position of the projection lens optical system, so that power consumption can be suppressed.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 includes an automatic focus detection device and an angle detection device according to the present embodiment, and focuses an image projected on a screen 1 by a projection lens optical system 8 of a projector 2 based on a focus position automatically detected. FIG. 2 is a schematic block diagram of a projector 2 that electrically corrects a trapezoidal distortion of an image projected on the screen 1 based on a detected relative tilt angle of the screen 1.
[0016]
The automatic focus detection device 20 according to the present embodiment includes a projection lens optical system 8 on the screen 1 via a pair of line sensors (31c and 31d, FIG. 10) in the imaging unit 31 of the line-type passive distance measuring device 3. Receives the image projected by. The outputs of the pair of line sensors (31c and 31d, FIG. 10) are sent to the calculation unit 22 in the automatic focus detection device 20. The calculation unit 22 measures high-frequency components or contrast data of the image signal output from the line sensor.
[0017]
The angle detection device according to the present embodiment detects a relative inclination angle of the projector 2 with respect to the screen 1 in a horizontal plane and a vertical plane. And a second line-type passive distance measuring device 4 for measuring distances to a plurality of positions arranged in a vertical direction. The line type distance measuring device has a pair of line sensors (31c and 31d, FIG. 10) in which a plurality of photodetector cells are linearly arranged as described later. The automatic focus detection device 20 receives an image on the screen 1 using the line sensor. The output of the line sensor is input to the calculation unit 22 of the automatic focus detection device 20. The automatic focus detection device 20 and the passive distance measurement devices 3 and 4 of the present embodiment do not emit or transmit light themselves, but are projected onto the screen 1 by the projection lens optical system 8 of the projector 2 by a method described later. The in-focus position and distance are measured by receiving the image.
[0018]
FIG. 2 is a plan view showing the configuration of the front of projector 2 shown in FIG. As shown in FIG. 2, a projection lens optical system 8 (which may include a condenser lens or the like) is provided in front of the projector 2, and projects an image on the screen 1. The first line-type passive distance measuring device 3 includes a pair of lenses 31a and 31b disposed on a plane constituting the front of the projector 2 and separated by a first base line length k (FIG. 11) extending in the horizontal direction. And an imaging unit 31 including Similarly, the second line-type passive distance measuring device 4 extends in the vertical direction orthogonal to the horizontal direction of the imaging unit 31 on the same plane that forms the front of the projector 2 and has a second base line length k ′ (not shown). It has an imaging unit 41 provided with a pair of lenses 41a and 41b that are arranged only apart from each other.
[0019]
Next, an automatic focus detection device 20 according to the present embodiment will be described with reference to FIGS. The arithmetic unit 22 of the automatic focus detection device 20 includes a high-pass filter (HPF) 22a that passes only high-frequency components or contrast data from image signals output from the pair of line sensors (31c and 31d, FIG. 10), a detector 22b, an A / D converter 22c, and an integrator 22d. When the power switch of the projector 2 is turned on or the like, the projector 2 takes out a pre-stored AF pattern (which may include a repetition pattern) suitable for the automatic focus from the projection image generation unit 6 and transmits the AF pattern to the transmission type liquid crystal display. The light is sent to the drive unit 7 and projected onto the screen 1 via the projection lens optical system 8. The optical system drive unit 23 includes a step motor and the like, and moves the projection lens optical system 8 back and forth along the optical axis direction to adjust the focus position of the image projected on the screen 1. That is, the automatic focus detection device 20 receives the image projected on the screen 1 by a pair of line sensors, and outputs a high frequency component or contrast data as shown in FIG. Send to control circuit 5. The control circuit 5 controls the optical system drive unit 23 and the projection lens optical system 8 based on the output from the calculation unit 22 of the automatic focus detection device 10 to perform automatic focus detection as described below, and adjusts the focus. Do.
[0020]
Next, with reference to FIG. 4, a focus position detection method by the automatic focus detection device 20 according to the present embodiment will be described. First, the projection lens optical system 8 is set at an initial position where an image projected from the projection lens optical system 8 when the power of the projector 2 is turned on is focused on the screen 1 at infinity. Then, the optical system driving unit 23 moves the focal position of the projection lens optical system 8 over the entire range from a focal position at infinity to a nearest focal position (a position determined by the projector, for example, 1 m). At this time, as shown in FIG. 4, the output from the arithmetic unit 22 increases the resolution of the image as the image on the screen 1 approaches the in-focus position, so that the high-frequency component or the contrast data increases. When the image on the screen 1 reaches the in-focus position, the high-frequency component becomes the highest, and thereafter the focus is defocused and the resolution is reduced, so that the high-frequency component is reduced. As described above, after moving the projection lens optical system 8 from the infinity focus position to the closest focus position and measuring the high frequency component or the contrast data, the projection lens optical system 8 is moved when the high frequency component or the contrast data reaches the maximum. The focus on the image on the screen 1 is adjusted by returning to the position from the closest focus position by the optical system driving unit 23. The in-focus position of the highest point is recorded by counting the drive time (or the number of step pulses) of the optical system drive unit 23 from the initial position at infinity.
[0021]
Next, an image adjusting method for a projector according to the present invention will be described with reference to FIG. As described above, when the power of the projector 2 is turned on (step 55), the focus of the image projected on the screen 1 is automatically adjusted (step 56). The focus adjustment is not limited to the time when the power is turned on, and can be changed as appropriate. For example, the focus adjustment may be automatically performed every predetermined time, or an AF switch (not shown) may be provided, and the focus adjustment may be performed when the AF switch is operated. As described above, according to the automatic focusing method of the present invention, as shown in the graph of FIG. 4, the image projected on the screen 1 is received by the light receiving sensor 21 while moving the projection lens optical system 8, and the best signal is obtained from the image signal. It is also called a hill-climbing autofocus (AF) because it detects a position where a high-frequency component (or the highest contrast data) is obtained.
[0022]
FIG. 6 shows the steps of the above-described automatic focusing method of the present invention in detail. After turning on the power, the automatic focusing operation is started. First, the projection lens optical system 8 is driven to an initial position (for example, a focal position at infinity) by the optical system driving unit 23. Here, contrast data detected by a pair of line sensors (31c and 31d, FIG. 10) of the angle detection device as high frequency components of the image signal is measured. In this specification, the description will be made assuming that the high-frequency component and the contrast data can be exchanged. The contrast data value (cont), the maximum contrast data value (Max_cont), the time when the contrast data has reached the maximum value (Tp), the recall time (Tr) (the time for returning the projection lens optical system 8 from the closest focus position to the initial position direction) Tr = Ti−Tp) are reset to zero (step 60). The feeding time Ti during which the projection lens optical system 8 is moved at a constant speed over the entire range from the initial position (focal position at infinity) to the closest focus position by the optical system driving unit 23 such as a step motor is set in advance.
[0023]
Next, an AF pattern suitable for the automatic focusing operation stored in advance in the projector 2 is projected onto the screen 1 via the projection lens optical system 8. Since the AF pattern does not measure the phase difference unlike the angle detection operation, it may be a repetitive pattern (step 61). The optical system driving unit 23 moves (projects) the projection lens optical system 8 from the initial position (focal position at infinity) to the latest focal position at a constant speed (at the same time, a pair of line sensors are projected on the screen 1 at the same time). Is received and the timer is operated (step 62). Each sensor data is read from the pair of line sensors (31c and 31d, FIG. 10) (step 63). Then, A / D conversion is performed on each sensor data (step 64). A contrast data (cont) value is calculated from each sensor data (step 65). Then, the average value of the respective contrast data (cont) obtained from the pair of line sensors (31c and 31d, FIG. 10) is obtained (step 66). It is determined whether the averaged contrast data (cont) value is larger than the maximum contrast data value (Max_cont) (step 67). If it is larger, the contrast data (cont) value is put into the maximum contrast data value (Max_cont), and the timer time Tp at that time is stored (step 68). Then, it is determined whether or not the current timer time has reached the extension time Ti required for moving the projection lens optical system 8 from the initial position (infinity focus position) to the latest focus position by the optical system drive unit 23 ( Step 69). If not, the process returns to step 63. If the contrast data (cont) value is not larger than the maximum contrast data value (Max_cont) (step 67), the process directly proceeds to step 69. If the current timer time has reached the extension time Ti, the movement of the projection lens optical system 8 by the optical system drive unit 23 is stopped (step 70), and the reversion for returning to the position of the maximum contrast data value is performed. The time Tr is calculated (Tr = Ti−Tp) (step 71). Then, the optical system driving unit 23 moves the projection lens optical system 8 from the closest focus position to the initial position (focal position at infinity) by the retraction time Tr (step 72). Then, whether or not the contrast data has the maximum value is detected again by the method of FIG. 7 (step 73). Note that the initial position and the driving direction of the projection lens optical system 8 are not limited to the above. For example, the initial position is set as the nearest focus position, the projection lens optical system 8 is moved from the initial position by the time Ti and driven to the infinity focal position, and is then moved out from the initial position by the time Tr to return to the position of the maximum contrast data value. May be.
[0024]
In this way, when the power of the projector 2 is turned on, the focus adjustment of the image projected on the screen 1 is performed. The projection lens optical system 8 projects an image on the screen 1 while moving the focal position, receives light by a pair of line sensors, measures high frequency components or contrast data of each image signal, and obtains an average value thereof. A position having the maximum high-frequency component or contrast data after the averaging process is detected as a focus position. For this reason, errors in mounting the pair of line sensors and errors due to the characteristics of the lens that forms an image on the pair of line sensors can be absorbed, the focus can be accurately determined to adjust the focus, and highly reliable autofocus can be performed. It becomes.
[0025]
Next, description will be made with reference to FIG. The method of FIG. 7 describes in detail the step of detecting the maximum value of the contrast data again (step 73) of FIG. That is, the projection lens optical system 8 is advanced by the predetermined number of steps (Ni_max) from the position returned in step 72 in FIG. Then, when the projection lens optical system 8 is extended, contrast data is measured again (step 74 and FIG. 8). Next, from the position returned in step 72 of FIG. 6, the projection lens optical system 8 is moved toward the infinity focal position by the predetermined number of steps (Nr_max). Then, when the projection lens system 8 is retracted, the contrast data is measured again (step 75 and FIG. 9). The predetermined number of steps (Nr_max) and (Ni_max) correspond to the movement of the projection lens optical system 8 from the in-focus position in FIG. 4 at a predetermined interval, and can be appropriately selected. For example, each can have 5 steps. Then, the maximum contrast data (Max_contI and Max_contR) measured in the respective steps 74 and 75 are compared (step 76), and the projection lens optical system 8 is moved to the position where the larger contrast data is measured (Nip). Step advance or Nrp step advance) (Step 77 or 78).
[0026]
FIG. 8 is a flowchart showing in detail the operation of step 74 in FIG. First, initialization is performed, and the Max_contI value, the cont value, the Nip value, and the n value are set to zero (step 81). Then, the projection lens optical system 8 is extended by one step toward the closest focus position, and 1 is added to the n value (step 82). Next, data is read out from the pair of line sensors (31c and 31d, FIG. 10), respectively, and sent to the calculation unit (22, FIG. 3) to perform processing such as A / D conversion to obtain contrast data. (Step 83). Thereafter, an average value of the pair of contrast data is obtained, and the averaged contrast data is substituted for the cont value (step 84). This cont value is compared with the Max_contI value (step 85). If the cont value is larger, the cont value is substituted for the Max_contI value, and the n value is substituted for the Nip value (step 86). Then, it is determined whether or not the n value has reached the Ni_max value (step 87). The Ni_max value is the maximum number of steps for extending the projection lens optical system in the direction of the closest focus position, for example, five steps. If it is determined in step 85 that the cont value is smaller than the Max_contI value, the flow directly proceeds to step 87. If the value n reaches the maximum number of extending steps Ni_max in step 87, the projection lens optical system 8 is advanced by the maximum number of extending steps Ni_max, that is, the projection lens optical system 8 is returned to the infinity focal position and returned to the initial position. Next, the operation shown in FIG. 9 is performed.
[0027]
FIG. 9 is a flowchart showing in detail the operation of step 75 in FIG. First, initialization is performed, and the Max_contR value, cont value, Nrp value, and n value are set to zero (step 91). Then, the projection lens optical system 8 is retracted by one step toward the focal position at infinity, and 1 is added to the n value (step 92). Next, data is read out from the pair of line sensors (31c and 31d, FIG. 10), respectively, and sent to the calculation unit (22, FIG. 3) to perform processing such as A / D conversion to obtain contrast data. (Step 93). Then, the average value of the contrast data from the pair of line sensors is calculated, and the contrast data after the averaging process is substituted for the cont value (step 94). This cont value is compared with the Max_contR value (step 95). If the cont value is larger, the cont value is substituted for the Max_contR value, and the n value is substituted for the Nrp value (step 96). Then, it is determined whether or not the n value has reached the Nr_max value (step 97). The Nr_max value is the maximum number of steps in which the projection lens optical system 8 is moved toward the infinity focal position, for example, five steps. If it is determined in step 95 that the cont value is smaller than the Max_contR value, the flow directly proceeds to step 97. If the value n has reached the maximum number Nr_max of recurring steps in step 97, the projection lens system 8 is advanced by the maximum number Nr_max of recurring steps, that is, the projection lens optical system 8 is returned to the direction of the latest focal point and returned to the initial position. Next, the operations from step 76 shown in FIG. 7 described above are performed.
[0028]
FIG. 21 is a graph for explaining the focusing operation shown in FIGS. 7 to 9. The projection lens optical system is extended from the infinity focus position to the closest focus position for the extension time Ti, and the extension time Tp at the time when the maximum contrast data or the average value of the high-frequency components is obtained from the pair of line sensors. Is stored, and when the extension time Ti has been reached, the projection lens optical system is stopped, and the projection lens optics is advanced from the closest focus position to the infinity focus position by the integration time Tr = Ti−Tp. Return the system to the position where the maximum contrast data or high frequency component was obtained. Then, a predetermined interval or a predetermined number of steps are used to extend and retreat the closest focus direction and the infinity focus direction from the returned position, and measure the contrast data or the high-frequency component. In search of the obtained position, the focal position of the projection lens optical system is readjusted. Even if the optical system driving unit 23 that drives the projection lens optical system 8 cannot accurately return the projection lens optical system 8 to the position of the maximum contrast data due to a movement error or the like, the area around the projection lens optical system 8 is projected. 8, the focus position having the maximum contrast data can be detected again to adjust the focus.
[0029]
Next, referring again to FIG. 5, after the focusing operation (step 56) is performed by the above-described hill-climbing autofocus, the relative inclination angle between the projector 2 and the screen 1 is detected by the angle detection device. Is detected, and the trapezoidal distortion is corrected (step 57). The angle detector uses a pair of line sensors to measure the phase difference between the received signals of the image projected on the screen 1 to measure the distance to the image on the screen, as described later. Since it is difficult to detect the phase difference in the image (1), a pattern different from the AF pattern may be used for angle detection. If both the AF pattern and the angle detection pattern do not include a repetitive pattern, both patterns can be unified, so that the configuration can be simplified. The image on the screen 1 has a relatively high contrast because the focus has already been adjusted in the previous step 56 of FIG. As a result, a highly accurate phase difference can be measured by the pair of line sensors of the angle detection device. Therefore, highly accurate distance measurement and angle detection can be performed, and trapezoidal distortion can be corrected with higher precision.
[0030]
During the trapezoidal distortion correction (step 57), the image on the screen 1 is shifted from the initial focus position. When the screen 1 has a relatively large screen, it may be desired to focus an image of a portion of the screen 1 (for example, a central portion) with particularly high precision. For this reason, the focus of the projection lens optical system 8 is adjusted based on the distance measurement data obtained by the phase difference detection method of the pair of line sensors (step 58). This focus adjustment (step 58) is different from the hill-climbing AF in step 56 of FIG. 5 in that the optical system driving unit 23 uses the projection lens based on the distance measurement data obtained by the phase difference detection method of the pair of line sensors. The focus position of the optical system 8 is adjusted from the first focus position. For this reason, the amount of movement remains within the range of fine adjustment. Therefore, it is possible to suppress power consumption accompanying movement of the projection lens optical system 8. In addition, this focus adjustment (step 58) is particularly effective when the projector projects on a large-screen screen because the center of the screen can be more accurately focused.
[0031]
Next, a method of detecting the relative inclination angle of the screen 1 by the angle detection device according to the present embodiment will be described with reference to FIG. 1 again. If the optical axis emitted from the projection lens optical system 8 to the screen 1 is in a positional relationship perpendicular to the screen 1 plane, the distance from the projection lens 8 to the top and bottom (or left and right) of the screen 1 is equal, No trapezoidal distortion occurs in the image on 1. However, in practice, the projector 2 is shifted downward or upward from the center of the screen so as not to obstruct the viewer when irradiating from the front of the screen 1. The projection optical axis irradiated to 1 is inclined from a position perpendicular to the plane of the screen 1.
[0032]
For this reason, the distance from the projection lens 8 is different between the upper and lower portions of the screen 1, and a trapezoidal distortion occurs in the image projected on the screen 1. As described above, in order to correct the trapezoidal distortion, the inclination of the optical axis of the projection lens 8 is optically corrected, or the portion projected small (large) due to the trapezoidal distortion is greatly enlarged (small reduced). Electrical correction is performed by an electric circuit to perform image processing. This electrical correction is described in Patent Document 2.
[0033]
In order to automatically perform these corrections, first, it is necessary to automatically and accurately measure the inclination angle at which the vertical direction of the screen 1 is inclined with respect to the optical axis of the projection lens 8.
[0034]
As will be described in detail below, the angle detecting device of the present embodiment includes first and second line-type passive distance measuring devices 3 and 4, and the horizontal (first By measuring the distance to a plurality of positions along the direction of the base line length of the line-type passive distance measuring device 3) and perpendicularly (corresponding to the direction of the base line length of the second line-type passive distance measuring device 4), the projector The relative tilt angle of the screen 1 with respect to 2 can be accurately measured in horizontal and vertical planes.
[0035]
The first and second line-type passive distance measuring devices 3 and 4 have operation units 32 and 42, respectively, and receive signals from the imaging units 31 and 41, respectively. Output signals from the operation units 32 and 42 are input to the control circuit 5. The control circuit 5 controls the first and second line-type passive distance measuring devices 3 and 4, and receives an input image from a device such as a personal computer (not shown) to output image information and a projection image generating unit 6; The transmission type liquid crystal display driving unit 7 that outputs an image to the projection lens optical system 8 is controlled. Further, the control circuit 5 receives an output from the calculation unit 22 of the automatic focus detection device 20, detects a focus position, and adjusts a focus position of the projection lens optical system 8 via the optical system drive unit 23. Further, the control circuit 5 calculates the relative tilt angles of the screen 1 with respect to the projector 2 in the horizontal direction and the vertical direction based on the outputs from the calculation units 32 and 42, respectively. Next, the control circuit 5 controls the projection image generation unit 6 and / or the transmission type liquid crystal display drive unit 7 based on the calculated inclination angle so as to correct the trapezoidal distortion, so that the screen 1 can be moved up and down and / or Alternatively, the image projected right and left is enlarged or reduced. As described above, the optical correction or the electrical correction itself of the trapezoidal distortion is known (for example, see Patent Document 2), and thus will not be described further. The control circuit 5, the operation unit 22, the operation units 32 and 42, and the memory unit 10 can be configured by one microprocessor (CPU) 9.
[0036]
The memory unit 10 stores data and instructions necessary for the configuration of the present invention, and supplies or receives data and instructions to the control circuit 5, the arithmetic unit 22, and the arithmetic units 32 and 42 as needed. The memory unit 10 includes two types of memory devices such as a non-volatile flash memory and a volatile RAM, and instructions and data used for a long time necessary for the present invention are stored in the non-volatile memory device. Data used only temporarily is stored in a volatile memory device.
[0037]
Next, the configuration of the angle detection device according to the present embodiment will be described with reference to the functional block diagram of FIG. For the sake of simplicity, only the configuration of the first line-type passive distance measuring device 3 will be described, but the second line-type passive distance measuring device 4 has the same configuration. Under a pair of lenses 31a and 32b horizontally separated by a base line length k (FIG. 11) on a plane constituting the front surface of the projector 2, a focal length f (FIG. 11) from these lenses 31a and 32b. And the line sensors 31c and 31d are arranged along the base line length k (horizontal) direction. The line sensors 31c and 31d are a pair of line CCDs having a predetermined number, for example, 104, of light detection elements (pixels) arranged in a straight line, or other line type imaging elements. From the imaging unit 31, an electric signal corresponding to the light amount of the image formed on each pixel of the line sensors 31c and 31d by the lenses 31a and 31b is output in series via the output unit 31e.
[0038]
The A / D conversion unit 32a converts an analog electric signal output from the output unit 31e of the imaging unit 31 into a digital signal. The digitized output signals from the line sensors 31c and 31d are stored in the memory area 32b as image data signal strings IL and IR, respectively, for subsequent processing. Accordingly, a pair of image data signal strings IL and IR each consisting of 104 data strings are stored in the memory area 32b. The memory area 32b may be provided in the memory unit 10.
[0039]
The filter processing unit 32c removes the DC component from the line sensor output signal (filing) and changes the image data signal trains IL and IR to a useful signal including only the spatial frequency component corresponding to the image. As will be described later with reference to FIGS. 11 and 12, the correlation operation unit 32d includes a partial image data group iLm (for example, 26 pixel groups spatially close to each other in the image data signal strings IL and IR). The reference image) and iRn (reference image) are selectively extracted, and the two partial image data groups iLm and iRn are compared with each other to calculate the degree of coincidence of data. For example, one partial image data group iLm is fixed as a reference unit, and the other partial image data group iRn is used as a reference unit, and the comparison is repeated with each pixel even in the IR even one pixel at a time. The maximum correlation degree detection unit 32e detects two partial image data groups iLm and iRn having the highest degree of data matching in the pair of image data signal strings IL and IR.
[0040]
The interpolation calculation unit 32f determines the position interval between the partial image data groups iLm and iRn having the highest degree of coincidence obtained by the maximum correlation degree detection unit 32e with a more accurate position than the position interval in pixel pitch units using a known interpolation method. Interpolate to intervals. Based on the position interval interpolated by the interpolation calculation unit 32f, the phase difference detection unit 32g determines the relative position of the pair of images of the same distance measurement target object formed on the pair of line sensors 31c and 31d. Calculate the phase difference (shift amount).
[0041]
As will be described later with reference to FIG. 19, the contrast centroid calculation unit 32h calculates the contrast centroid of the images formed on the line sensors 31c and 31d. The reliability determination unit 32i determines the reliability of the calculated relative phase difference (shift amount) between the positions imaged on the two line sensors 31c and 31d. This reliability determination is performed, for example, if the object whose distance is to be measured is correctly imaged on both line sensors 31c and 31d, the coincidence obtained by the maximum correlation detection unit 32e is equal to or greater than a predetermined value. Should be. Therefore, even if the degree of coincidence obtained by the maximum correlation degree detection unit 32e is relatively high, if the degree of coincidence is less than a predetermined value, the reliability is determined to be low, and the reliability determination unit 32i determines that the degree of reliability is low. Eliminate the result. If the degree of coincidence obtained by the maximum correlation degree detection unit 32e is equal to or greater than a predetermined value, it is determined that the data is reliable and CONF_FLG1 = OK. The configurations of the imaging unit 31 and the calculation unit 32 described above are well known, and are described in, for example, Patent Literature 3 and Patent Literature 4. Therefore, further description will be omitted.
[0042]
[Patent Document 3]
Japanese Patent No. 3230759 [Patent Document 4]
Japanese Patent Publication No. 4-77289 [0043]
Further, the angle detection device according to the present embodiment includes a mutual reliability determination unit 51 for determining the reliability of the distance measurement result of a small group of several spatially adjacent measurement positions, and a spatially adjacent number of An average calculator 52 for calculating an average value of the distance measurement result and the center of gravity of the contrast with respect to the small group at the measurement position, and an angle calculator 53 for calculating an inclination angle from the distance measurement result are included. Based on the tilt angle of the screen 1 calculated by the angle calculation unit 53, a correction amount for correcting trapezoidal distortion is given to the projection image generation unit 6 and / or the display drive unit 7. Thus, the trapezoidal distortion on the screen 1 is corrected.
[0044]
When the line sensors 31c and 31d are used instead of the light receiving sensor 21 of the automatic focus adjustment device 20, the outputs of the line sensors 31c and 31d from the output unit 31e in FIG. You can also send it to
[0045]
Next, the operation principle (external light triangulation method) of the line type passive distance measurement device 3 will be described with reference to FIG. The first line-type passive distance measuring device 3 includes a pair of lenses 31a and 31b extending in a horizontal direction on a plane constituting the front of the projector 2 and separated by a base length k, and the lenses 31a and 31b from the base length k. And a pair of line sensors 31c and 31d extending along the same horizontal direction as the base line length k direction at a focal distance f. The first line type passive distance measuring device 3 measures the distance between a base line length k and a plurality of positions on the plane of the screen 1 located in a plane including the line sensors 31c and 31d, and determines the base line length k and the line sensor. The relative inclination angle of the screen 1 plane with respect to the projector 2 in the plane including 31c and 31d is calculated.
[0046]
For the sake of simplicity, only the first line-type passive distance measuring device 3 will be described here, and the description of the second line-type passive distance measuring device 4 will be omitted. The description also applies to the second line type passive distance measuring device 4 only by replacing the horizontal direction with the vertical direction.
[0047]
In FIG. 11A, a pair of lenses 31a and 31b are spaced apart from each other by a predetermined base line length k extending in the horizontal direction on a plane constituting the front surface of the projector 2. A pair of line sensors 31c and 31d separated from the pair of lenses 31a and 31b by their focal length f and extending in the base line length k direction (horizontal direction) are provided below a plane constituting the front surface of the projector 2. Are located. The line sensors 31c and 31d are arranged such that their central portions are located substantially on the optical axes 31ax and 31bx of the lenses 31a and 31b, respectively, and the corresponding lenses 31a and 31b As a result, an image 1A at a certain position on the screen 1 to be measured is formed. In FIG. 11A, the measurement position 1A on the screen 1 is imaged on the line sensors 31c and 31d through the optical paths A and B in different directions, via the respective lenses 31a and 31b. .
[0048]
If it is assumed that the measurement position 1A is located at infinity, the measurement position 1A is located on the line sensors 31c and 31d located at the focal length f from the pair of lenses 31a and 31b. An image is formed at reference positions 31cx and 31dx crossing the axes 31ax and 31bx.
[0049]
Next, when the measurement position 1A approaches from the infinity position along the direction A on the optical axis 31ax of the lens 31a, and reaches the position of FIG. 11A, that is, the distance LC, the measurement position 1A is placed on the line sensor 31c. In, the image is still formed on the reference position 31cx, but is formed on the line sensor 31d by the lens 31b at a position shifted from the reference position 31dx by a phase difference (shift amount) α.
[0050]
From the principle of triangulation, the distance LC to the measurement position 1A is determined by LC = kf / α. Here, the base line length k and the focal length f are known values that are known in advance. If the phase difference (shift amount) α from the reference position 31dx on the line sensor 31d is detected, the distance LC can be measured. This is the principle of operation of a passive line sensor distance measuring device for external light triangulation. The detection of the phase difference (shift amount) α and the calculation of LC = kf / α are executed by the calculation unit 32 in FIG.
[0051]
The detection of the phase difference (shift amount) α from the reference position 31dx of the line sensor 31d is performed by detecting the partial image data groups iLm and iLm extracted from the pair of image data signal strings IL and IR output from the pair of line sensors 31c and 31d, respectively. The operation unit 32 detects iRn by performing a correlation operation. This correlation operation is well known (for example, see Patent Document 3).
[0052]
For this reason, a detailed description of the correlation calculation is omitted, and only the following brief description will be given. As shown in FIG. 11B, in the correlation operation, the area where the degree of coincidence is highest when the partial image data groups iLm and iRn are overlapped with each other is determined by using the partial image data groups iLm and iRn to be overlapped with the line sensors 31c and 31d. This is an operation for detecting while shifting relatively. In FIG. 11B, the partial image data group iLm from one of the line sensors 31c is fixed at a reference position 31cx and used as a reference portion. The position of the partial image data group iRn from the other line sensor 31d is shifted by one pixel as a reference portion, and a partial image data group iRn having the highest matching degree with the reference portion is searched for. The interval between the position on the line sensor 31d that generates the partial image data group iRn having the highest matching degree and the reference position 31dx of the line sensor 31d is the phase difference (shift amount) α.
[0053]
Each of the line sensors 31c and 31d is composed of a pair of line CCDs in which a predetermined number of photodetector cells (pixels) are arranged on a straight line of a predetermined length, as will be described later with reference to FIG. The phase difference (shift amount) α can be easily obtained from the pixel position and the pixel pitch in the image data signal sequence IR of the partial image data group iRn. In this way, the distance LC to the measurement position 1A in the same direction A as the optical axis 31ax of the lens 31a can be measured by detecting the phase difference (shift amount) α.
[0054]
Next, the principle of measuring the distances LR ′ and LR to the measurement position 1B in a different direction from FIG. 11 will be described with reference to FIG. As shown in FIG. 12A, an image of the measurement position 1B is formed on the line sensors 31c and 31d through the optical paths C and D in different directions, via the lenses 31a and 31b, respectively.
[0055]
If it is assumed that the measurement position 1B exists at infinity in the direction C to be measured, the center of the image at the measurement position 1B formed on the pair of line sensors 31c and 31d by the pair of lenses 31a and 31b is The reference positions 31cy and 31dy are separated from each other by the base line length k. Next, when the measurement position 1B at the infinity position approaches along the distance measurement direction C and reaches the position shown in FIG. 12A, the image at the measurement position 1B formed by the lens 31a is displayed on the line sensor 31c. Does not change, but the position of the image at the measurement position 1B formed by the lens 31b on the line sensor 3dc is shifted from the reference position 31dy by a phase difference (shift amount) α ′.
[0056]
From the principle of triangulation, the distance LR to the measurement position 1B is LR = kf / (α′cosβ). The angle β is a tilt angle of the distance measurement direction C with respect to the vertical line of the base line length k, that is, the optical axis 31ax of the lens 31a, and is an angle determined by determining the measurement direction C. Since the base line length k, the focal length f and the cos β are known values, the distance LR can be measured by detecting the phase difference (shift amount) α ′.
[0057]
The distance LR ′ from the same plane (base line length k) constituting the front of the projector 2 on which the lenses 31a and 31b are arranged to the measurement position 1B is obtained by LR ′ = LRcosβ = kf / α ′. That is, the distance LR ′ can be obtained from the known base line length k and focal length f by detecting the phase difference (shift amount) α ′. That is, the angle β is unnecessary for measuring the distance LR ′.
[0058]
In order to detect the phase difference (shift amount) α ′, the above-described correlation calculation is performed. As shown in FIG. 12B, the position is fixed using the partial image data group iLm corresponding to the reference position 31cy from one line sensor 31c as a reference part, and the partial image data group iRn from the other line sensor 31d is fixed. The reference portion iRm having the data with the highest matching degree with the data of the reference portion iLm is found by shifting the position as a reference portion by one pixel and overlapping each other.
[0059]
Each of the line sensors 31c and 31d is composed of a pair of line CCDs in which a predetermined number of photodetector cells (pixels) are linearly arranged at a predetermined length as described later with reference to FIG. The phase difference (shift amount) α ′ is calculated from the position (pixel number) in the image data signal sequence IR of the partial image data group iRn and the position (pixel number) in the image data signal sequence IL of the partial image data group iLm and the pixel pitch. It can be easily obtained.
[0060]
In the above-described correlation calculation method, the partial image data group iLm from one line sensor 31c is fixed as a reference unit, and the partial image data group iRn from the other line sensor 31d is used as a reference unit and the position is set to one pixel. It is said that the degree of coincidence is inspected by shifting each other. However, when the distance measurement direction is a direction from the intermediate position between the lenses 31a and 31b, the position of the partial image data groups iLm and iRn is moved in the opposite direction on the line sensors 31c and 31d. The group iLm and iRm may be inspected for a high degree of matching with each other.
[0061]
Next, one of the pair of line sensors 31c and 31d will be described in detail with reference to FIG. The other line sensor 31d is configured similarly to the line sensor 31c. The line sensor 31c is configured by a linear CCD (charge coupled device) in which a large number of, for example, 104 photodetector cells (pixels) are linearly arranged, or another linear imaging device. The 104 photodetector cells (pixels) are assigned pixel numbers in order from the left end to the right end in the figure. In these photodetector cells (pixels), seven distance measurement calculation areas are divided into 31c1 (1-26), 31c2 (13-38), 31c3 (27-52), and 31c4 (39) by a group of adjacent 26 units. 64), 31c5 (53 to 78), 31c6 (65 to 90) and 31c7 (79 to 104). Here, the numbers in parentheses are the photodetector cell (pixel) numbers. Each of the distance measurement calculation areas 31c1 to 31c7 has the first half of the 26 photodetector cells included in the distance measurement calculation area adjacent to the front and the latter half included in the distance measurement calculation area adjacent to the rear. The distance calculation areas 31c1 to 31c7 overlap the adjacent distance measurement calculation areas by half each other.
[0062]
The signals from the photodetector cells (pixels) in each of the distance measurement calculation areas 31c1 to 31c7 correspond to each partial image data group iLm of the image data signal sequence IL of the line sensor 31c in FIGS. Each of the center positions a (13), b (26), c (38), d (52), e (64), f (78) and g (90) of each of the distance measurement calculation areas 31c1 to 31c7 is (however, , The number in parentheses is the pixel number), which is the reference position for determining the distance measurement direction. As a result, the distance measuring device 3 using the line sensors 31c and 31d according to the present embodiment measures the distance to the seven separated positions on the screen 1 in the same plane (horizontal plane) as the reference line k. be able to. However, the actual distance measurement direction can be corrected by the contrast centroid position in the distance measurement calculation area by the contrast centroid calculation unit 32h in FIG. FIG. 13 shows reference positions a ', b', c ', d', e ', f', and g 'corresponding to the other line sensor 31d. It is used when calculating a shift amount when performing a correlation calculation with the distance calculation area.
[0063]
The plurality of different positions on the screen 1 for which the distance is to be measured according to the present invention need not be limited to seven, but may be an appropriate number, for example, 11 or the number of pixels of the line sensors 31c and 31d or the distance measurement operation area Can be selected by appropriately selecting the number.
[0064]
For example, 11 distance measurement calculation areas may be provided in units of 27 photodetector cell (pixel) groups using a line CCD having 162 photodetector cells (pixels). In each area, 13 to 14 pixels out of the 27 pixels are used in an overlapping manner with the adjacent distance measurement calculation area. In this example, one of 11 positions along the reference line direction (horizontal direction) on the screen 1 can be selected.
[0065]
Next, description will be made with reference to FIG. FIG. 14 shows a state where the mutual positional relationship between the screens 1 of the projector 2 is set to a predetermined positional relationship in order to perform initial adjustment of the line type distance measuring devices 3 and 4. That is, the screen 1 is previously set in parallel with the base lengths k and k ′ (not shown) so that the projection optical axis from the projection optical lens system 8 of the projector 2 is perpendicular to the screen 1. An image suitable for initial adjustment of the mold distance measuring devices 3 and 4 is projected. The initial adjustment means, for example, that the lenses 31a and 31b have aberrations. For this reason, when different measurement positions along the base line length k direction on the screen 1 are imaged on the line sensors 31c and 31d, they are actually distorted instead of being formed on a straight line. In the initial adjustment, a correction coefficient for correcting the distortion due to the lens aberration is calculated, stored in the memory unit 10, and used by the calculation units 32 and 42 thereafter. The line-type distance measuring device 3 measures the distances on the screen 1 in the seven distance-measuring directions using the seven distance-measuring calculation areas 31c1 to 31c7 on the line sensor 31c. For simplicity, in FIG. 14, out of the seven directions, 1C, 1E, and 1G on the screen 1 in three ranging directions corresponding to the three ranging calculation areas 31c3, 31c5, and 31c7 on the line sensor 31c. Only the position is shown.
[0066]
Next, a method of measuring the relative inclination angle of the screen 1 using the passive line distance measuring device 3 will be described with reference to FIGS. For the sake of simplicity, the two distance measurement directions C and G of the two distance measurement calculation areas 31c3 and 31c7 of the line sensor 31c are used, and two distance measurement directions C and G on the screen 1 in the two distance measurement directions C and G are used. Two distances LR ′ and LL ′ to the two measurement positions 1C and 1G are measured by the method described with reference to FIG. In the present embodiment, only two distances LR ′ and LL ′ are measured, but actually, distances to seven measurement positions on the screen 1 in seven distance measurement directions are measured.
[0067]
If the measurement positions 1C and 1G on the screen 1 are images suitable for passive distance measurement, an image including a logo of a projector manufacturer projected on the screen 1 via the projection lens 8 of the projector 2 may be used. Also, when the angle detection operation is performed periodically during the operation of the projector 2, the measurement positions 1C and 1G on the screen 1 may be any images projected on the screen 1.
[0068]
The distance L between the reference positions c (38) and g (90) in the distance measurement directions C and G of the two distance measurement calculation areas 31c3 and 31c7 of the line sensor 31c is determined by the pixel number and pixel pitch in parentheses. This is a known value.
[0069]
Assuming that a point perpendicularly lowered from the measurement position 1C on the straight line k2 parallel to the base line length k to a straight line k1 parallel to the base line length k passing through the measurement position 1G is C ′, between the measurement positions 1C and C ′ Is equal to LR′−LL ′. When the inclination angle θ1 of the screen 1 is not so large, the point of the distance LR′−L / f from the measurement position 1G on the straight line k1 is C ″, and the magnitude of LR′−LL ′ is C ′. The distance 1C'-C "when the intersection point 1C 'between the screen 1 and the line orthogonal to the straight line k1 from" is obtained. Usually, the relative positional relationship between the screen 1 and the projector 2 is manually set in advance. Is often adjusted, the inclination angle θ1 does not become very large, and this approximation is appropriate in many cases.The triangle formed by the measurement position 1G and the point C ″ and the center of the lens 31a and the reference The triangle formed by the positions c and g and the center of the lens 31a have a similar relationship, and the two reference positions c (38) and g (90) of the two distance measurement calculation areas 31c3 and 31c7 on the line sensor 31c. ) Distance between L, since then corresponds to the distance between the measurement position 1G~ point C ", the value of the inclination angle θ1, using the relationship and trigonometric functions similar shape,
θ1 = arctan {(LR′−LL ′) / (LL ′ * L / f)}
You can ask.
[0070]
Therefore, the control circuit 5 of the projector 2 can calculate the inclination angle θ1 of the screen 1 and the projector 2 in the base line length k direction in the horizontal plane by performing the above equation. The control circuit 1 in FIG. 1 can give an instruction to correct the trapezoidal distortion of the image to the projection image generation unit 6 and / or the display drive unit 7 based on the magnitude of the inclination angle θ1. However, the inclination angle θ1 obtained from the above equation depends on the accuracy of the distance measurement results LR ′ and LL ′ to the measurement positions 1G and 1C.
[0071]
In FIG. 15, the measurement distances are replaced with the lengths of the vertical lines LR ′ and LL ′ lowered in the base line length k direction from the measurement positions 1C and 1G, and the distances along the distance measurement directions C and G from the lens 31a. The length may be up to the measurement positions 1C and 1G. This case will be described with reference to FIG.
[0072]
If high accuracy is required for angle detection, each distance measurement calculation area 31c3 and 31c7 used for angle detection is replaced by the distance L between the reference values c (38) and g (90). The distance of the position of the center of gravity of the contrast in the distance calculation areas 31c3 and 31c7 may be used.
[0073]
Referring to FIG. 19, distance measurement using the position of the center of gravity of the contrast by the contrast center of gravity calculation unit 32h of FIG. 10 will be described. As is well known, passive distance measurement includes an operation of detecting a location having the highest matching degree when a pair of images formed on two line sensors are superimposed. This is to detect whether or not the contrast states of the images match.
[0074]
Therefore, in the passive type distance measurement, if the designed distance measurement direction of one distance measurement operation area 31cn is the direction of the arrow J as shown in FIG. 19, an image is formed on the distance measurement operation area 31cn. If the image to be measured is an image in which the contrast position 1K exists only in the arrow K direction, the actual distance measurement direction is shifted from the arrow J direction to the arrow K direction. If the distance measurement target image formed on the distance measurement calculation area 31cn is an image in which the contrast position 1M exists only in the arrow M direction, the actual distance measurement direction is shifted from the arrow J direction in the arrow M direction. . Further, when the image of the distance measurement target formed on the distance measurement calculation area 31cn is an image in which the contrast positions 1K and 1M exist in the arrow K direction and the arrow M direction, the actual distance measurement direction is from the arrow J direction. The image is shifted to the position of the center of gravity of the contrast of the image formed on the measurement calculation area 31cn.
[0075]
Therefore, by using the distance of the position of the center of gravity of the contrast in each distance measurement calculation area as a value corresponding to the distance between the two distance measurement calculation areas used for angle detection, a highly accurate distance L can be used. The angle detection accuracy is improved. The method of determining the position of the center of gravity of the contrast is described in Patent Document 5 and is well known.
[0076]
[Patent Document 5]
JP-A-8-75985
For reference, Equation 1 for obtaining the position of the center of gravity of the contrast in the present embodiment is shown below.
[0078]
(Equation 1)

Here, L (): sensor data Sa on the reference portion 31c side: light receiving element minimum No. on the reference portion 31c side.
Wn: number of light receiving elements in the subgroup t; integer (generally 1 to 4)
In order to cancel the influence of noise, when the absolute value of the difference is equal to or less than a predetermined value (noise cancellation level), the difference is not added to the sum.
The light receiving elements (pixels) arranged in one line of the line sensor 31c have a series of serial numbers (pixel numbers).
[0079]
Next, with reference to FIG. 20, a description will be given of a method of calculating the inclination angle θ1 using the passive line distance measuring device 3 according to another method. As shown in FIG. 20, the inclination angle of the screen 1 with respect to the base line length k of the line-type passive distance measuring device 3 (horizontal direction of the projector 2) is set to θ1, and the distance measurement of the line sensor 31c is performed by the method described with reference to FIG. The distance to the screen 1 calculated by the distance measurement along the distance measurement direction of the calculation area 31c7 is L1, and the distance to the screen 1 calculated by the distance measurement along the distance measurement direction of the distance calculation area 31c3. The distance is assumed to be L2. The angle formed by the distance measurement direction of the previously known distance measurement calculation area 31c3 and the direction perpendicular to the base line length direction is β, and the angle between the previously known distance measurement calculation area 31c7 and the base line length direction is the same. The angle formed by the vertical direction is γ. The inclination angle θ1 is calculated by the following equation.
[0080]
θ1 = arctan (L2cosβ−L1cosγ) / (L1sinγ + L2sinβ)
[0081]
In this way, the control circuit 5 shown in FIG. 10 calculates the tilt angle of the screen 1 and corrects the trapezoidal distortion of the image on the screen 1 based on the obtained tilt angle. As described above with reference to step 58 in FIG. 5, after correcting the trapezoidal distortion, the distance from the projector 2 to the screen 1 is measured by the distance measuring device 3 to adjust the focus of the projection lens optical system 8. Do it again. Specifically, for example, the control circuit 5 outputs a signal based on the focal position of the projection lens optical system 8 corresponding to the distance to the screen 1 measured by the distance measuring device to the optical system driving unit 23, and drives the optical system. The unit 23 performs focus adjustment by driving the projection lens optical system 8 to the focus position. This corrects the focus fluctuation after the trapezoidal distortion correction, and in the case of a relatively large screen, focuses the projection lens optics so that the image at a specific location on the screen, for example, the center position, is particularly focused. To readjust. This readjustment requires only a small adjustment with a small movement from the in-focus position by the hill-climbing AF in step 56 of FIG. 5 of the projection lens optical system 8, and power consumption can be suppressed.
[0082]
Note that, instead of the hill-climbing AF in step 56 in FIG. 5, when the power is turned on, a distance measurement operation by phase difference measurement using a pair of line sensors of the distance measurement device 3 is performed, and focusing is performed based on the distance measurement data. If the adjustment is made, the focus detection device 20 may not be required. However, it is considered that the image on the screen is out of focus at the initial stage such as when the power is turned on in step 55, and the contrast of the image on the screen is low. Therefore, the accuracy of the phase difference detected by the pair of line sensors of the distance measuring device 3 is low, and the accuracy of the distance measurement result is also low, and the focus adjustment cannot be accurately performed by the pair of line sensors of the distance measuring device 3. Is considered to occur. If the contrast of the image on the screen is low, the accuracy of the subsequent angle detection is also low, and there is a high possibility that the trapezoidal distortion correction in step 57 will not be accurate. Therefore, the focusing adjustment in step 56 in FIG. 5 performs the hill-climbing AF as shown in FIGS. 4 and 6 in which the projection lens optical system 8 is moved to detect the high frequency component or the contrast data of the image projected on the screen. Is preferred.
[0083]
【The invention's effect】
As described above, according to the projector of the present invention described in claim 1, an image projected on a screen using a pair of line sensors for angle detection does not require a separate light emitting element. It can perform both trapezoidal distortion correction and automatic focusing (autofocus).
[0084]
According to the projector of the second aspect of the present invention, it is possible to absorb the mounting error of the pair of line sensors and the error due to the characteristic of the lens that forms an image on the pair of line sensors, and to obtain the in-focus position accurately. Adjustment is possible, and highly reliable autofocus is possible.
[0085]
According to the projector of the third aspect of the present invention, the optical system driving unit for driving the optical system of the projection lens is located at a position where the image signal is accurately maximized by one operation due to a movement error or the like. Even if the image signal cannot be returned, the projection lens optical system is moved in both directions by a predetermined distance near the maximum image signal, and the position where the image signal is maximum is measured again to accurately adjust the focus position. can do.
[0086]
According to the method of the present invention, since the focus position of the image projected on the screen of the projection lens optical system is first adjusted, the image used for correcting the trapezoidal distortion is also reduced. It is focused and projected on the screen. For this reason, the images received by the pair of line sensors have high contrast, and thus a high phase difference can be obtained. As a result, the distance from the projector to a plurality of locations of the image projected on the screen can be measured with relatively high accuracy, and the relative tilt angle of the screen can be obtained with relatively high accuracy. Keystone distortion can be corrected with high accuracy. Further, the focus shift due to the trapezoidal distortion correction can be corrected by the distance measurement operation using the pair of line sensors after the trapezoidal distortion correction.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram showing a configuration of a projector according to one embodiment of the present invention.
FIG. 2 is a schematic front view of the projector shown in FIG.
FIG. 3 is a functional block diagram of a calculation unit of the automatic focus detection device according to one embodiment of the present invention.
FIG. 4 shows the focus position of a projection lens optical system of a projector on a horizontal axis to explain an automatic focusing method according to one embodiment of the present invention, and shows an image projected on a screen by the projection lens optical system. 4 is a graph in which a vertical axis indicates a high frequency component (or contrast data) included in a light receiving signal.
FIG. 5 is a flowchart illustrating a method for adjusting an image of a projector according to an embodiment of the present invention.
FIG. 6 is a flowchart illustrating an automatic focusing method according to one embodiment of the present invention.
FIG. 7 is a flowchart illustrating an automatic focusing method according to another embodiment of the present invention.
FIG. 8 is a flowchart showing details of an automatic focusing method according to the embodiment of FIG. 7;
FIG. 9 is a flowchart showing details of an automatic focusing method according to the embodiment of FIG. 7;
FIG. 10 is a functional block diagram of an angle detector according to one embodiment of the present invention.
FIG. 11 is a diagram illustrating a distance measuring operation of the distance measuring device included in the angle detector according to one embodiment of the present invention.
FIG. 12 is another diagram illustrating a distance measuring operation of the distance measuring device included in the angle detector according to one embodiment of the present invention.
FIG. 13 is a block diagram schematically showing a pair of line sensors of a distance measuring device included in the angle detector according to one embodiment of the present invention.
FIG. 14 is a view for explaining distance measurement at a plurality of positions by a distance measuring device included in the angle detector according to one embodiment of the present invention.
FIG. 15 is a diagram illustrating an angle detection method by a distance measuring device included in the angle detector according to one embodiment of the present invention.
FIG. 16 is a view for explaining an angle detection method by the distance measuring device included in the angle detector according to one embodiment of the present invention.
FIG. 17 is a diagram illustrating an angle detection method by a distance measuring device included in the angle detector according to one embodiment of the present invention.
FIG. 18 is a diagram illustrating an angle detection method by a distance measuring device included in the angle detector according to one embodiment of the present invention.
FIG. 19 is a view for explaining a method for obtaining the position of the center of gravity of the contrast of the ranging operation area of the ranging device included in the angle detector according to one embodiment of the present invention.
FIG. 20 is a view for explaining an angle detection method by the distance measuring device included in the angle detector according to one embodiment of the present invention.
FIG. 21 illustrates a focus position of a projection lens optical system of a projector on a horizontal axis to explain an automatic focus adjustment method according to another embodiment of the present invention, and shows an image projected on a screen by the projection lens optical system. 4 is a graph in which a vertical axis indicates a high frequency component (or contrast data) included in a light receiving signal.
[Explanation of symbols]
1 Screen 2 Projector 3 Distance measuring device 4 Distance measuring device 5 Control circuit 8 Projection lens optical system 20 Automatic focus detection device 22 Operation unit 23 Optical system drive unit 31 Imaging unit 31a Lens 31b Lens 31c Line sensor 31d Line sensor 32 Operation unit k Baseline length θ1 Inclination angle of screen 1 with baseline length k in horizontal plane

Claims (4)

An angle detection device including a projection lens optical system for projecting an image on a screen, a pair of line sensors for correcting trapezoidal distortion of an image projected on the screen by the projection lens optical system, and the projection lens optical system The focal point of the projection lens optical system is moved to the position where the image signal obtained by receiving the projected image by the pair of line sensors while moving the focal position of the system is maximized. A projector comprising an automatic focus detection device for adjusting. The projector according to claim 1, wherein the automatic focus detection device measures an average value of the image signals received by the pair of line sensors. The automatic focus detection device adjusts the focal position of the projection lens optical system to a position where the image signal is maximum, and then moves the projection optical lens system by a predetermined interval from the position to the direction of the farthest focus position and the closest focus position. 3. The projector according to claim 1, further comprising: measuring again a position where an image signal obtained by receiving an image projected on the screen while moving in the direction and obtaining a maximum image signal, and adjusting a focus position again. A method of adjusting an image projected on a screen by a projection lens optical system, comprising: projecting an image on the screen while moving a focal position of the projection lens optical system; Measuring the position where the image signal obtained by receiving light by the line sensor is maximum, adjusting the focal position of the projection lens optical system at the maximum, and adjusting the focal position of the pair of the projection lens optical systems after the adjustment. Measuring a distance to an image projected on the screen using a line sensor to calculate a relative inclination angle of the screen to correct trapezoidal distortion of the image; and correcting the trapezoidal distortion. Measuring the distance to the image projected on the screen using the pair of line sensors after the step, and Image adjustment method comprising a step of adjusting the focal position again.

Images