JP2003348499A - Projection type image display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of a conventional technique that has caused a sense of incongruity to a viewer even when trapezoidal distortion is corrected if the viewer does not confront the screen. <P>SOLUTION: The projection type image display apparatus is provided with: a correction information arithmetic means for calculating correction information to correct image distortion so that a projected image in an oblique direction with respect to a projected screen can be viewed as almost a rectangular image from a direction confronting the center of the projected image; and a corrected information correction means for correcting the corrected information calculated by the correction information arithmetic means on the basis of a projection condition so that the projected image in the oblique direction can be viewed as almost a rectangular image from directions other than the direction confronting the center of the projected image. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type image display device such as a projector or a large-screen television, and more particularly to correction of so-called trapezoidal distortion of a screen.

[0002]

2. Description of the Related Art In recent years, liquid crystal projectors (hereinafter abbreviated as projectors) have attracted attention as projection-type image display devices that satisfy the needs of a large screen, small size, thin shape, and light weight.

In such a projector, there is a problem of trapezoidal distortion in which the screen is distorted into a trapezoidal shape when the direction of the normal to the screen surface and the direction of the optical axis of the projection light are shifted.

For example, as shown in FIG. 9, when the projector main body 122 is installed at an elevation angle from the horizontal (so that the optical axis 124 is inclined), an image (screen) projected on the screen 101 is the same as the projected image 117. Will be distorted into a trapezoidal shape.

As a method for automatically correcting such trapezoidal distortion, Japanese Patent Application Laid-Open No. Hei 8-09309 discloses a method of measuring the distance between a projector and at least three points on a screen surface to determine the inclination of the screen surface. There has been proposed a method of correcting trapezoidal distortion by detecting and projecting image data that cancels out distortion of a display image.

Japanese Unexamined Patent Application Publication No. 2001-186538 proposes a method of automatically detecting trapezoidal distortion by detecting the inclination of the screen surface from the projection angle of the projection light and the installation angle of the projector main body.

[0007]

By the way, according to the conventionally proposed automatic trapezoidal distortion correction method, the projected image on the screen is corrected so as to be rectangular (rectangular) from the direction directly facing the screen. The purpose is. That is, when the observer faces the center of the screen, the observer can observe an image without a rectangular distortion.

However, under conditions where the observer is not directly facing the screen, such as when the observer looks up at the image projected on the screen or observes the image obliquely from the side, a portion of the projected image that is farther from the observer. Looks shrunk. In particular, when projecting onto a large screen or when projecting with a projector body at an elevation angle, the center of the screen is often higher than the viewpoint of the observer. In this case, since the upper end of the screen is far from the observer, the image projected on this portion appears in a reduced state.

Furthermore, in such a case, the observer tends to be less sensitive to trapezoidal distortion than when facing the screen surface, and a slightly enlarged upper end of the screen provides a more natural image. You will be able to observe. Therefore, it is necessary to correct the trapezoidal distortion correction according to the observation situation of the observer.

Therefore, the present invention provides a projection type image display device which can perform an image observation without a sense of incongruity by performing distortion correction of a projection image in consideration of an actual observation position of an observer. The purpose is.

[0011]

In order to achieve the above object, according to the projection type image display device of the present invention, a projected image obliquely to a surface to be projected faces the center of the projected image. Correction information calculating means for calculating correction information for correcting image distortion so as to be observable as a substantially rectangular image from the direction, and a direction other than the direction in which the projected image from the oblique direction is directly opposite to the center of the projected image Correction information correction means for correcting the correction information calculated by the correction information calculation means on the basis of the projection condition on the projection surface so that the image can be observed as a substantially rectangular image.

[0012] The correction information calculation means uses a method similar to the conventional one or the like to trapezoidal distortion or the like so that a substantially rectangular image is observed when the projected image is observed from the direction directly opposite the center of the projected image. Correct image distortion. Then, the correction information correction means assumes, for example, a situation in which the observer observes the image projected on the projection surface by looking up obliquely from below, so that a substantially rectangular image can be observed in the observation situation.
For each projection condition on the projection surface such as the tilt angle of the device, the angle between the device and the projection surface obtained from the distance between the device and the projection surface at multiple points, and the variable magnification state of the projection optical system that can change the magnification. Based on the correction information, the correction amount of the image distortion by the correction information calculating means is corrected.

Thus, even when the observer is not directly facing the center of the projected image, the observer can observe the image without feeling uncomfortable.

The correction information calculated by the correction information calculation means so that the projected image becomes a trapezoidal substantially rectangular image in which a portion farther from the observation position in the projection image is larger than a portion closer to the observation position. May be corrected. Specifically, it is preferable that an image of a slightly trapezoidal shape (a trapezoidal distortion rate to be described later is several percent) is obtained by enlarging a portion farther from the observation position than a portion closer to the observation position. This allows the observer to observe a more natural image.

[0015] Further, there may be provided a selection means for selecting whether to activate or deactivate the correction information correcting means.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, an automatic trapezoidal distortion correction function of a liquid crystal projector (projection image display device) will be described.

FIG. 1 shows a configuration of a liquid crystal projector having only a trapezoidal distortion correction function, which is a premise of the present invention.

An image signal is input to the projector main body 22 through an input terminal 10 from an image information supply device such as a personal computer, video, DVD player, or the like.

The input image signal is converted into a digital image signal by an A / D converter 8, and the converted digital image signal is input to an image processing circuit 7.

The image processing circuit 7 temporarily stores the digital image signal, and electrically performs processing such as scaling of the image and correction of image distortion under the control of the CPU 9.

The image-processed digital signal is converted into an analog image signal by a D / A converter 6 and supplied to a liquid crystal drive circuit 5.

The liquid crystal drive circuit 5 is a circuit for displaying an input image on the liquid crystal panel 3. When an image is displayed on the liquid crystal panel 3, the irradiation light from the lamp 4 arranged on the back of the liquid crystal panel 3 is modulated into image light representing the image. The image light is magnified and projected on the screen 1 via the projection lens system 2 arranged in front of the liquid crystal panel 3.

The projection lens system 2 includes a focus lens 2a that moves in the optical axis direction for focusing, a zoom lens 2b that moves in the optical axis direction to change the magnification, and a condenser lens 2c.

Here, there are generally two methods for correcting trapezoidal distortion of a projected image, an electrical correction method and an optical correction method. The electric trapezoidal distortion correction method is as follows. An image having a trapezoidal distortion opposite to the projected image is displayed on the display surface of the liquid crystal panel 3 by the image processing circuit 7, and the image is projected by the projection lens 2, whereby the screen 1 is projected. The above is a method of displaying a substantially rectangular image with almost no trapezoidal distortion.

In the optical trapezoidal distortion correction method, a substantially rectangular image with almost no trapezoidal distortion is displayed on the screen 1 by adjusting the inclination of the light beam of the condenser lens 2c in the projection lens system 2. The way to do it.

Here, an electrical trapezoidal distortion correction method will be described. In order to perform automatic trapezoidal distortion correction, it is necessary for the trapezoidal distortion detection circuit 13 to detect trapezoidal distortion information of an image on a screen surface. As a method of detecting trapezoidal distortion information, there are a method of measuring the distance between the projector main body 22 and a plurality of points on the screen 1 with a distance sensor, a method of measuring the inclination angle of the projector main body 22, and the like.

A trapezoidal distortion correction amount calculation circuit 12 in the CPU 9 calculates a trapezoidal distortion correction amount based on the detection information from the trapezoidal distortion detection circuit 13.

The electrical trapezoidal distortion correction method will be described in more detail. FIG. 4 shows the projector main body 22.
And the relationship between the screen 1 and the facing surface 1 ′ with respect to the projection direction.

In both the method of measuring the distance between the projector main body 22 and a plurality of points on the screen 1 and the method of measuring the inclination angle θ of the projector main body 22, the actual screen 1 and the facing surface 1 are measured. The trapezoidal distortion is detected by finding the angle θ between the 'and'.

When the trapezoidal distortion detection circuit 13 is a distance sensor for measuring the distance between the projector main body 22 and the screen 1, as shown in FIG. 3, both end points E and E 'on the screen 1 from the projection position O. Distance (beam length of the projected light) b and c can be measured. Furthermore, if the projection angle of view A is known, the angle θ formed between the screen 1 and the facing surface 1 ′ which is a virtual surface facing the center of the projector main body 22 can be calculated by the following equation.

[0031]

(Equation 1)

In the case where the trapezoidal distortion detecting circuit 13 measures the installation angle (tilt angle) of the projector main body 22, if it is known that the screen 1 is installed vertically or at a constant angle with respect to the horizontal axis. For example, the inclination angle of the projector main body 22 can be obtained by detecting the direction of the gravitational acceleration using an acceleration sensor.

For example, as shown in FIG. 5, the direction of the gravitational acceleration G in the horizontal state is measured in advance and stored in a memory (not shown) in the CPU 9, and the acceleration sensor ( (Not shown) to detect the direction of the gravitational acceleration G actually acting on the device,

[0034]

(Equation 2)

By calculating
Can be obtained.

In FIG. 4, when the upper side length of the image (screen) before the trapezoidal distortion correction is X, the lower side length is Y, the upper side length of the screen after the trapezoidal distortion correction is T, and the lower side length is V, T The relationship between X and V and Y is as follows: T = αX V = βY

Here, α represents the trapezoidal distortion correction amount on the upper side of the screen, and β represents the trapezoidal distortion correction amount on the lower side of the screen. The trapezoidal distortion correction amount calculation circuit 12 in the CPU 9 uses the detected inclination angle θ to calculate the trapezoidal distortion correction amounts α and β.
Is calculated. The calculation formula is as follows.

[0038]

(Equation 3)

[0039]

(Equation 4)

Here, p and q are lens shift amounts indicating the distance from the center of the screen to the upper and lower sides of the screen, respectively. In a projector, the optical axis 24 is generally shifted downward from the center of the screen. In this case,
p> q.

Further, in the present embodiment, the trapezoidal distortion rate is defined as (1 / α-1) × 100 [%]. The distortion rate after the trapezoidal distortion correction is desirably ± 1% or less.

The trapezoidal distortion correction amount calculating circuit 12 calculates correction amounts α and β so as to correct the trapezoidal distortion of the image projected on the screen 1. In practice, it is necessary to correct the trapezoidal distortion while maintaining the aspect ratio by multiplying the magnification for each line of the image.

The image processing circuit 7 performs image processing for each line by a predetermined method on the basis of the calculation result of the trapezoidal distortion correction amount calculation circuit 12.

For example, a digital image signal for canceling the trapezoidal distortion is generated by thinning out or adding data by a predetermined dot for each horizontal line of the liquid crystal panel 3 in accordance with the result of the correction amount calculation. At this time, the digital signal is processed so that the aspect ratio of the projected image becomes a predetermined ratio such as 4: 3 or 16: 9.

Further, by detecting the zooming state (zoom magnification) of the projection lens system 2 by the zoom encoder 11,
It is also possible to perform more accurate trapezoidal distortion correction.

The digital signal subjected to the trapezoidal distortion correction is converted into an analog image signal by the D / A converter 6,
The image is supplied to the liquid crystal drive circuit 5 and the image after the trapezoidal distortion correction processing is displayed on the liquid crystal panel 3. As a result, the image is projected on the screen 1 so that it looks like a rectangle when viewed from the direction directly opposite to the center of the image.

In the trapezoidal distortion correction processing described above, processing is performed so that the image projected on the screen 1 becomes rectangular when viewed from the direction directly facing the center of the image. In this case, a good rectangular image can be observed, but when the observer looks up at the screen from the bottom while sitting in a chair or the like, the upper part of the projected image is more observable than the lower part. Since it is far from (the position of the observer's eyes), it is seen in a reduced state, and makes the observer feel uncomfortable. Therefore, it is necessary to correct the trapezoidal distortion correction amount.

FIG. 2 shows the configuration of a projector according to the present invention which also has a trapezoidal distortion correction amount correcting function.
In this projector, a correction amount correction circuit 15 and a trapezoidal distortion correction target value determination circuit 18 are added to the CPU 9 shown in FIG. Also, a trapezoidal distortion detection circuit 19 having an inclination angle detector 14 and a distance detector 17 and a correction amount correction operation selection switch 16 are added to the apparatus of FIG. Note that components other than these newly added components are the same as the components of the apparatus in FIG. 1 and are denoted by the same reference numerals.

The tilt angle detector 14 is constituted by an acceleration sensor, and detects the gravitational acceleration G. And the detector 14
Is obtained, the installation angle (inclination angle) θ of the projector main body 22 is obtained. This is, as described in FIG. 5, that the direction of the gravitational acceleration G in the horizontal state of the apparatus is measured in advance, and the direction of the gravitational acceleration G actually acting on the installed projector main body 22 is detected. Thus, the installation angle (inclination angle) θ of the projector main body 22 can be obtained.

The distance detector 17 is constituted by a distance sensor of an infrared triangulation system or the like, and measures a plurality of distances between a plurality of points on a screen (projected surface) and the projector body 22. Then, as described in FIG. 3, the installation angle θ of the projector main body 22 with respect to the screen 1 can be obtained from the measured distance. The correction amount correction circuit 15
The correction amount calculated by the trapezoidal distortion correction amount calculation circuit 12 is corrected. The correction amount is calculated based on the output value of the zoom encoder 11, the output value of the distance detector 17, and the output value of the tilt angle detector 14 that detects the tilt angle of the projector main body 22. Note that the zoom encoder 11 is obtained from table data stored in advance in a ROM provided in the CPU 9 or the like.
Output value, the output value of the distance detector 17 and the inclination angle detector 1
The correction amount may be selected based on the output value of No. 4.

The trapezoidal distortion correction target value determination circuit 18 determines the final trapezoidal distortion correction target from the correction amount output from the trapezoidal distortion correction amount calculation circuit 12 and the correction amount output from the correction amount correction circuit 15. Determine the value. However, if it is selected by the correction amount correction operation selection switch 16 not to perform the correction operation, the correction amount is set to 0 and the trapezoidal distortion correction is directly performed using the calculation result of the trapezoidal distortion correction amount calculation circuit 12.

The trapezoidal distortion correction operation in this embodiment will be described with reference to the flowchart of FIG.

First, trapezoidal distortion correction processing is started when the projector is activated or when an instruction to start an automatic trapezoidal distortion correction operation is given in response to a user operating a switch.

[Step (abbreviated as S in the figure) 101] Here, the trapezoidal distortion correction amount calculation circuit 12 first executes FIG.
The trapezoidal distortion is corrected by the method described above using the method described above or another method so that a projection image oblique to the screen 1 can be observed as a rectangular image from a direction directly opposite to the center of the projection image. Is calculated for the correction.

[Step 102] Here, it is determined whether or not the operation for correcting the trapezoidal distortion correction amount is selected (ON) by the selection switch 16 (OFF). If the selection switch 16 is ON, the process proceeds to step 103,
If it is OFF, the process proceeds to step 108. By providing this step 102, the user can arbitrarily select ON / OFF of the correction amount correction operation. For example,
In a case where the observer observes the screen 1 (image) directly, the correction amount correction operation may be turned off.

[Step 103] Here, an initial value P of the correction amount of the trapezoidal distortion correction amount is set. The initial value P is set as a value indicating how much the projector is to be corrected in a horizontal state where trapezoidal distortion does not occur and in a predetermined zoom state such as a telephoto end. In the case of elevation projection, it is necessary to correct the upper side to be longer, so that P> 0,
When projecting the screen upside down, such as in a ceiling mount,
P <0. Suspended installation will be described later.

[Step 104] Here, the zoom state of the projection lens system 2 is detected using the encoder 11 (hereinafter, the detected value is referred to as a zoom encoder value Z).

[Step 105] Here, the inclination angle of the projector main body 22 is determined by the inclination angle detector 14 composed of an acceleration sensor and the distance detector 1 composed of a distance measuring sensor.
7 (hereinafter, the calculated value is referred to as a projector inclination angle θ).

[Step 106] Here, the correction amount correction circuit 15 reads the zoom encoder value Z and the projector tilt angle _θ and converts them into coefficients W _Z and W _θ for weighting the correction amount. W _Z is a weighting factor as a function of the zoom encoder value Z, and W _θ is a weighting factor as a function of the tilt angle θ. Conversion methods include a method of converting table data into respective coefficients, and a method of performing conversion using a calculation formula.

The reason why the zoom encoder value Z and the inclination angle θ are detected in step 104 and step 105 is that the correction amount of the trapezoidal distortion correction amount changes depending on such information. For example, when the image is projected with the zoom set to the wide side, the screen is projected to be large, so it is better to increase the correction amount.
In addition, when the inclination angle is large, it is conceivable that the use condition is such that an observer looks up at the screen 1.
It is desirable to increase the amount of correction. Therefore, the relationship between Z and θ and the weighting factors W _Z and W _θ can be expressed as shown in FIG. That is, the weighting factors W _Z and W _θ are increased as _Z and _θ are increased.

[Step 107] Here, the correction amount of the trapezoidal distortion correction amount is obtained by the correction amount correction circuit 15. When the correction amount is obtained by calculation, if the correction amount is M, it can be expressed by the following equation.

[0062]

(Equation 5)

[Step 108] Here, the trapezoidal distortion correction target value determination circuit 18 determines the final trapezoidal distortion correction target from the trapezoidal distortion correction amount calculated in step 101 and the correction amount obtained in step 107. Determine the value.
If the target value is C,

[0064]

(Equation 6)

Can be represented by

That is, the final target value C of the trapezoidal distortion correction is set to the original correction amounts α and β, the correction amount initial value P, and the weighting factors W _Z and W _θ corresponding to the zoom state and the inclination angle.
Is calculated as a function of

In step 102, the correction amount correction operation is turned off.
In the case of, the initial value of the correction amount is set to P = 0.

It should be noted that the target value is not obtained by calculation as in step 108, but the target value is stored in the ROM as table data.
It is also possible to read out the target value for each correction amount.

[Step # 109] Here, the final target value C for trapezoidal distortion correction determined in step 108 is sent to the image processing circuit 7. Thereby, the image processing circuit 7
Is

[0070]

(Equation 7)

The upper side length T is determined so that The lower side length V remains at V = βY described above.

The image processing circuit 7 performs a process for each line of the liquid crystal panel 3 based on the target value C, and projects an image which cancels a trapezoidal distortion large enough to make a viewer feel uncomfortable.

As described above, the projected image when the projector is projected from the lower side of the screen at an elevation angle, the upper side is considerably larger than the lower side as shown in a projected image 91 shown in FIG. Although it becomes a long trapezoid, when the trapezoidal distortion correction based on the calculation result in step 102 is performed,
As shown in a projection screen 93 shown in FIG.
The image becomes a rectangle when viewed directly from the image.

Further, by performing the operation of correcting the trapezoidal distortion correction amount shown in steps 103 to 109, FIG.
As shown in a projection screen 94 shown in (c), a few% (for example, 2 to 5)
%). This allows
Close to the projector body 22 and the projector body 2
When observed at a position 90 at almost the same height as 2, an image (a trapezoidal substantially rectangular image) that can be observed most naturally (without feeling uncomfortable) can be projected on the screen.

Up to this point, a description has been given of the usage state in which the projector main body 22 is installed on a table or the like and an image is projected at an elevation angle. However, in addition to this, the case where the projector main body is used by hanging it from a ceiling or the like is also considered. Can be In the suspended state, the image is automatically or manually inverted by image processing so that the image observed by the observer does not turn upside down.

In this case, in the trapezoidal distortion correction in step 102, since the inclination angle θ of the projector main body 22 is negative, the trapezoidal distortion correction amount is determined using the absolute value of θ.
Furthermore, in this case, the correction of the trapezoidal distortion correction amount must be reversed on the upper side and the lower side from the case of elevation projection,
What is necessary is just to invert the sign of the initial value P of the correction amount of the trapezoidal distortion correction.

As described above, the modified initial value P is adjusted so as to match various use conditions (projection conditions) of the projector.
And the weight coefficient W _Z is a function of zoom information, than to determine the weighting factor W _theta is a function of the tilt angle, it is possible to realize a projection type image display apparatus to meet the needs of the viewer.

In the above embodiment, the correction operation for correcting the trapezoidal distortion in the horizontal direction performed when looking up the projected image from below has been described. However, the present invention is applicable to the case where the observer views the projected image from the horizontal direction. The present invention can also be applied to a projection-type image display device that performs an operation of correcting a vertical keystone distortion correction to be performed.

It is also possible to simultaneously correct the vertical and horizontal trapezoidal distortion corrections.

Further, in the above embodiment, the case where the trapezoidal distortion correction amount is corrected based on the installation angle of the apparatus and the zoom state has been described.
The trapezoidal distortion correction amount may be corrected based on the information. For example, the present invention is particularly effective when the arrangement relationship between the projection unit and the projection surface is fixed, such as a large-screen television.

[0081]

As described above, according to the present invention,
Even when an image on the projection surface is observed from a direction that does not face the center of the image, an image that can be observed without discomfort can be projected.

[Brief description of the drawings]

FIG. 1 is a block diagram of a liquid crystal projector having an automatic keystone distortion correction function, which is a prerequisite technology of the present invention.

FIG. 2 is a block diagram of a liquid crystal projector having a trapezoidal distortion correction function according to an embodiment of the present invention.

FIG. 3 is a diagram for explaining a method of detecting the inclination angle of the projector.

FIG. 4 is a diagram for explaining a method of calculating a trapezoidal distortion correction amount in the projector.

FIG. 5 is a diagram for explaining a method of obtaining a projector tilt angle from an acceleration sensor.

FIG. 6 is a flowchart of a trapezoidal distortion correction operation according to the present invention.

FIG. 7 is a diagram illustrating a relationship example between a zoom encoder value Z and an inclination angle θ and weighting coefficients W _Z and Wθ.

FIG. 8 is a diagram illustrating a state of a projection screen before, after, and after correction of trapezoidal distortion by the projector.

FIG. 9 is a diagram illustrating trapezoidal distortion of a projected image.

[Explanation of symbols] 1 screen 2 Projection lens 2a Focus lens 2b zoom lens 2c condenser lens 3 LCD panel 4 lamp 5 LCD drive circuit 6 D / A converter 7 Image processing circuit 8 A / D converter 9 CPU 10 Input terminal 11 Zoom encoder 12 Keystone distortion correction amount calculation circuit 14 Tilt angle detector 15 Correction amount correction circuit 16 Correction amount correction operation selection switch

Claims (6)

[Claims] 1. A projection-type image display device for projecting an image on a projection surface, wherein a projection image oblique to the projection surface is a substantially rectangular image from a direction directly opposite to the center of the projection image. Correction information calculating means for calculating correction information for correcting image distortion so as to be observable as a projected image, and a projected image from the oblique direction is a substantially rectangular image from a direction other than a direction directly facing the center of the projected image. And a correction information correcting means for correcting the correction information calculated by the correction information calculating means based on the projection condition so as to be observable as a projection image display apparatus. 2. The correction information correction unit according to claim 1, wherein the correction unit is configured to correct the projection image so as to be a trapezoidal substantially rectangular image in which a portion far from the observation position in the projection image is larger than a portion near the observation position. 2. The projection type image display device according to claim 1, wherein the correction information calculated by the information calculation means is corrected. 3. The apparatus according to claim 1, further comprising a detecting unit configured to detect an inclination angle of the projection type image display device, wherein the correction information correcting unit is operated by the correction information calculating unit based on the inclination angle detected by the detecting unit. The projection type image display device according to claim 1, wherein the correction information is corrected. 4. A detecting means for detecting a distance between the projection type image display device and a plurality of points on the projection surface, wherein the correction information correcting means detects a plurality of distances detected by the detecting means. 2. The correction information calculated by the correction information calculation means based on the correction information.
3. The projection type video display device according to 1. 5. A variable magnification projection optical system, and detection means for detecting a variable power state of the projection optical system, wherein the correction information correcting means changes the variable power state detected by the detection means. 2. The projection type image display device according to claim 1, wherein the correction information calculated by the correction information calculation means is corrected based on the correction information. 6. The projection type image display device according to claim 1, further comprising a selection unit for selecting whether to activate or deactivate the correction information correction unit.