JP4266724B2 - Projector having tilt angle measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projector, and more particularly to a projector having an inclination angle measuring device for calculating an inclination angle between an optical axis of a projection device of a projector to be used and a projection surface.
[0002]
[Prior art]
With the rapid development of liquid crystal technology and DLP (digital light processing) technology, the miniaturization and high performance of projectors have expanded the use of projectors for image projection, and large-scale replacements for display-type televisions at home. It is also attracting attention as a display device.
[0003]
However, unlike a display-type television, a projector has a problem that an image is distorted due to the relative relationship between the optical axis of the projector and the projection surface because the image surface is a screen or a wall. Japanese Patent Laid-Open No. 9-281597 has a projector installation angle detection means and a distance detection means for detecting the distance between the projector and the projection target, and the angle of the liquid crystal display unit is calculated based on the angle calculated from both detection results. A method of adjusting is disclosed. In this case, it is necessary to mechanically adjust the angle of the liquid crystal display unit. Japanese Patent Application Laid-Open No. 2001-169221 discloses that a light point of a laser pointer capable of angle control is projected on a curved screen, while a point image for measurement is generated, projected from the projector onto the screen, and photographed with a camera. Coordinate conversion parameter memory by replacing the pixel coordinates on the frame memory of the point image with the coordinates on the input image of the light point when the points coincide with each other while moving the point image by measuring the position of the light spot and the point image Distortion correction methods set in the above are disclosed. In this case, it is necessary to control the angle of the laser pointer, and the structure becomes complicated.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-281597 [Patent Document 2]
[Patent Document 1] Japanese Patent Laid-Open No. 2001-169 211
[Problems to be solved by the invention]
On the other hand, when the vertical and horizontal inclinations of the screen with respect to the optical axis of the projector are known, a technique for projecting an image without distortion by converting the coordinates of the frame memory of the projector has been put into practical use. As a method for detecting the tilt of the projector with respect to the image, a horizontal or vertical test pattern projected from the projector is photographed with an image sensor placed away from the projection lens, and the tilt of the projector relative to the screen is determined from the tilt of the photographed test pattern. There is a method of detecting, but in this case, a table in which the difference between the number of pixels corresponding to the intersection of the test pattern and both ends of the imaging screen is calculated and the difference pixel number and the inclination angle created in advance are associated with each other is calculated. In this method, the inclination angle is calculated by 1 of the image sensor. With higher accuracy than hydrogen it was not possible to detect the inclination of the test pattern.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to provide a projector having a tilt angle measuring device that can accurately measure the tilt angles in the vertical and horizontal directions with respect to the optical axis of the projector for correcting image distortion. .
[0007]
[Means for Solving the Problems]
The liquid crystal projector having the tilt angle measuring device of the present invention is
The projector has a tilt angle measuring device that calculates the tilt angle between the projection optical axis of the projector and the projection surface, and corrects distortion of the image on the projection surface by controlling the output video of the image display unit according to the calculated tilt angle. Projector. The tilt angle measurement device includes a test pattern generation device, a digital camera, and an image analysis tilt angle calculation unit. The imaging lens of the digital camera is arranged on the irradiation side surface of the projector in the vertical and horizontal directions from the projection lens of the projection device. Projection devices project test patterns in the vertical and horizontal directions with respect to the projection surface so that an image is formed near the edge of the digital camera's imaging screen in the tilt angle calculation mode. The test pattern is composed of a plurality of white and black straight lines alternately arranged at intervals of one dot of the image sensor of the digital camera, and the image analysis inclination angle calculation unit projects the projection imaged by the digital camera. The slope of the test pattern on the surface is taken as the difference in the number of pixels at the intersection of the test pattern and both ends of the imaging screen if the slope is greater than a predetermined angle If the inclination is equal to or smaller than a predetermined angle, the state of change on the dod line of the moire brightness generated on the dod line is obtained by the intersection angle between the test pattern and the dod line, and the difference in the number of pixels and Analyzing the inclination angle between the test pattern and the reference line indicating the vertical and horizontal directions of the projector from the state of change in brightness, and determining the inclination angle between the projection optical axis of the projector and the projection surface from the inclination angle Calculate.
[0008]
The image sensor of the digital camera is preferably an image sensor having a VGA (video graphic array) resolution of 640 × 480 dots.
[0009]
The analysis of the tilt angle between the test pattern captured by the digital camera and the reference line from the imaging screen of the imaging device of the digital camera is based on the difference pixel number of both dots corresponding to the intersection of the test pattern and both ends of the imaging screen. And the inclination angle may be calculated by a table in which the difference pixel number and the inclination angle created in advance are associated with each other, and the moire generated on the dod line by the intersection angle between the test pattern and the dod line may be calculated. Analysis of the tilt angle between the test pattern and the reference line indicating the vertical and horizontal direction of the projection device from the change of the brightness of the test pattern on the dodd line, matched one end of the black line of the test pattern with one end of the dod line When there is a peak of the upper limit of the luminance value on the dot line, the total number of dots on the dot line is set to the dot between the center and one end of the peak of the upper limit. The value divided by the number is the number of dots between the two ends of the test pattern imaging screen. When there is no peak luminance value on the dot line, the end opposite to one end The number of pixels divided by the brightness value corresponding to the white line is the number of dots as the number of dots between the two ends of the test pattern imaging screen. The tilt angle may be calculated using a table.
[0010]
The control of the output video of the video display unit according to the tilt angle between the projection optical axis and the projection surface of the projection device of the projector is based on the correction value of the input video of the video display unit calculated in advance corresponding to the tilt angle. It may be executed by creating a control parameter and controlling the projector image processing LSI.
[0011]
The projector may be a liquid crystal projector or a DLP (Digital Light Processing) projector.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram of a projector having a tilt angle measuring apparatus according to an embodiment of the present invention. FIG. 2 is a schematic explanatory diagram of a projector having a tilt angle measuring apparatus of the present invention. Is a schematic side view showing a projection state, (b) is a schematic front view of the projector, (c) is a schematic diagram of an imaging screen of the digital camera, and FIG. 3 is a view from the projection device to the projection surface in the tilt angle measurement mode. It is a schematic diagram of the test pattern projected, (a) is a vertical line test pattern, (b) is a horizontal line test pattern.
[0013]
Here, a liquid crystal projector will be described as an example, but the present invention can be similarly applied to a DLP (digital light processing) projector by replacing the liquid crystal display unit 22 with a DLP display unit.
[0014]
The projector 10 includes a projection device 20 having a projection lens 21 and a liquid crystal display unit 22, an image control unit 23 that controls an image of the liquid crystal display unit 22, an inclination angle measuring device 30, and a CPU 60 that controls the overall operation. The tilt angle measuring device 30 includes a test pattern generating device 40, an imaging lens 51, a digital camera 50 having an image sensor 52 having a resolution of 640 × 480 dots VGA (video graphic array), and an image captured by the image sensor 52. An image analysis inclination angle calculation unit 53 that analyzes pixels and calculates vertical and horizontal inclinations of the projection apparatus 20 with respect to the projection plane 70;
[0015]
As shown in FIG. 2A, the projector 10 is usually arranged on the pedestal 90 so as to be inclined in the vertical direction so that an image is projected onto a projection surface 70 such as a screen or a wall. In this case, when projection is performed in a state where the projection optical axis 26 of the projection device 20 of the projector 10 and the projection surface 70 are orthogonal to each other, the screen of the liquid crystal display unit 22 is enlarged and projected onto the projection surface as it is. When the plane orthogonal to the projection optical axis 26 and the projection plane 70 are inclined, the distance from the projection lens 21 changes depending on the position as compared with the case where the plane is orthogonal, for example, the screen is enlarged because the screen is enlarged at a distant position. There arises a problem that a trapezoidal distortion occurs on the screen. In order to solve this problem, for example, a device as described in the above-mentioned patent document has been made. In this case, if the inclination angle between the projection plane 70 and the vertical plane with respect to the projection optical axis 26 of the projection device 20 can be accurately grasped, the projection plane is obtained by moving the arrangement of the image of the liquid crystal display section 22 to the pixels by the image control section 23. The image projected on 70 can be corrected to the correct state, and the mobility can be obtained numerically from the tilt angle by a known technique.
[0016]
The object of the present invention is to accurately grasp the inclination angle between the projection optical axis 26 of the projection apparatus 20 and the projection surface 70, and the object is achieved by the inclination angle measuring apparatus 30 described below.
[0017]
In the tilt angle measurement mode, the test pattern generation device 40 of the tilt angle measuring device 30 controls the image control unit 23 to generate the vertical line test pattern 83a and the horizontal line test pattern 83b shown in FIG. Project to. As shown in FIG. 3, the vertical line test pattern 83a and the horizontal line test pattern 83b are alternately provided with white and black straight lines so that the image sensor 52 has an interval of twice the dot interval on the imaging screen 80. Is controlled. The projection position can be adjusted by the image control unit 23 such that the image analysis tilt angle calculation unit 53 analyzes the imaging screen 80 of the digital camera 50 to obtain a desired position. As shown in FIG. 2B, the projection lens 21 and the imaging lens 51 are desirably arranged so as to be separated in the vertical direction and the horizontal direction.
[0018]
FIG. 2C shows an imaging screen 80 when the vertical line test pattern 83a and the horizontal line test pattern 83b projected on the projection surface 70 are imaged by the imaging device 52 of the digital camera 50. The projection surface 70 has a projection lens at the top. 2, the upper side of the vertical line test pattern 83a is lower in the image of the image sensor 52 taken at a position away from the projection lens 21 in the horizontal direction, as shown in FIG. It is displayed at a position on the right side of the side. Similarly, although not shown in the figure, the projection surface 70 is inclined in the direction away from the projection lens 21 on the left side, and therefore, in the image of the image sensor 52 taken at a position away from the projection lens 21 in the vertical direction, the horizontal line test is performed. The pattern 83b is displayed at a position where the left side is higher than the right side.
[0019]
The image analysis tilt angle calculation unit 53 analyzes the vertical line test pattern 83a and the horizontal line test pattern 83b on the imaging screen 80 from the respective pixels, and the upper and lower sides of the projection optical axis 26 and the projection surface 70 of the projection device 20 by a predetermined calculation formula. Direction and left / right tilt angles are calculated and output to the image control unit 23. The image control unit 23 moves the arrangement of the image on the liquid crystal display unit 22 to pixels according to a predetermined calculation formula based on the tilt angles. The video projected on the projection surface 70 is corrected to the correct state.
[0020]
FIG. 4 is a schematic flowchart showing a standard process of correcting the output video of the liquid crystal display unit 22 from the difference pixel number. The image analysis inclination angle calculation unit 53 acquires the difference pixel number information about the difference pixel number 86 in the vertical direction and the difference pixel number 87 in the horizontal direction on the same line from the imaging screen 80 of the imaging element 52 (step S11). Is used to generate an inclination angle between the optical axis of the projection device 20 and the projection surface 70 (step S12), and the image control unit 23 generates an LSI control parameter in response to the generated inclination angle (step S13). By controlling the image processing LSI (step S14), the input video 24 is modified to become an output video 25 on the liquid crystal display unit 22. When the output video 25 is projected onto the projection surface 70, it becomes a video similar to the input video 24.
[0021]
In this method, when the inclination between the projection surface 70 and the vertical plane of the projection optical axis 26 is large, the number of difference pixels 86 and 87 is also large, so the accuracy of the correction of the output image 25 is high, but the degree of inclination is small and the number of difference pixels is small. There is a problem that fine adjustment cannot be performed when 86 and 87 approach 1. Therefore, in the present embodiment, the test pattern is a black-and-white repeating straight line having the same width, and is projected onto the projection surface 70 so that the interval between the center line of the black line and the white line becomes the dot interval of the captured image.
[0022]
5 and 6 are schematic diagrams showing moire appearing in the dot row when the direction of the dot row of the captured image and the direction of the test pattern are tilted, taking the horizontal line test pattern as an example, and FIG. 5B and FIG. 5B show the case where the dot pattern direction and the test pattern direction are inclined by 0.5 × dot interval at both ends of the dot line. When the direction of the row and the direction of the test pattern are inclined by 1.0 × dot interval at both ends of the dot row, FIG. 5D shows that the direction of the dot row and the direction of the test pattern are 1.5 × dot at both ends of the dot row. When the interval is inclined, FIG. 6 (e) shows the direction of the dot row and the direction of the test pattern is 2.0 × dot interval inclined at both ends of the dot row, and FIG. 6 (f) shows the direction of the dot row and the test pattern. Direction is at both ends of the dot row 2.5 × when tilted dot spacing, shown in FIG. 6 (g) shows a case where the direction of the direction and the test pattern of the dot array is inclined 3.0 × dot spacing on both ends of the dot array. The upper row shows the display state of the test pattern imaging screen, the middle row shows the state of one dot row, and the lower row shows the luminance change of the dot row and the number of dots up to the maximum value. Here, an image sensor 52 having a resolution of 640 × 480 dots VGA (video graphic array) is used. In the figure, the black and white lines are clearly separated and displayed on the dot for ease of explanation, but the dot at the position where the black line and the white line of the dot line are mixed is actually displayed at the average brightness at that position. As a result, the dodd line is a gradation of white and black, and it becomes a moire state.
[0023]
As described above, when a change in luminance of a dot line is detected by matching a black line with a dot line at one end, the dot interval of the lowest and highest luminance changes corresponding to the inclination, and the inclination is 1.0 dot / When L is greater than or equal to L, the highest luminance value appears in the middle, so the value obtained by dividing the total number of dots of the line by the minimum and highest luminance dot spacing is the difference in dots at both ends, that is, the number of difference pixels, and the slope is at both ends. In the case of 1 dot or less between them (inclination <1.0 dot / L), the luminance value at the end changes without the highest luminance value appearing in the middle due to the inclination, so the luminance value at the end is the luminance value of the white line. The divided value becomes the difference of dots at both ends, that is, the number of difference pixels, and a minute inclination of the test pattern can be detected.
[0024]
Specifically, assuming that an image sensor having a gradient of 3.0 dots / L in FIG. 6G is captured by an image sensor having a resolution of VGA, the total number of horizontal dots of the image sensor is 640 dots, The position difference from the lowest luminance dot is 213 dots. Accordingly, the inclination is 640 ÷ 213 = 3.00 dots / L at both ends of the image sensor, that is, the difference pixel number is 3.00. In this case, if the positional difference between the highest luminance and the lowest luminance is shifted by 1 dot,
640 ÷ 212 = 3.02 dots / L
640 ÷ 213 = 3.00 dots / L
640 ÷ 214 = 2.99 dots / L
Therefore, the inclination can be detected with very high accuracy of 1 to 2% of the dot interval.
[0025]
FIG. 7 is a schematic flowchart showing a standard process for correcting the output image of the liquid crystal display unit 22 from the brightness value at the dot interval / end of the lowest and highest brightness. The image analysis tilt angle calculation unit 53 matches the black line of the test pattern with the dot line at one end from the imaging screen 80 of the imaging element 52 and detects the change in the brightness of the dot line in units of dots. The ratio of the luminance dot interval or the luminance value at one end to the luminance value of the white line is acquired (step S21), and the tilt angle between the projection optical axis 26 and the projection surface 70 of the projection device 20 is generated based on this ratio (step S22). In response to the generated tilt angle, the image control unit 23 generates an LSI control parameter (step S23), and controls the projector image processing LSI (step S24), whereby the input video 24 is modified and the liquid crystal display unit 22 becomes an output image 25. When the output video 25 is projected onto the projection surface, the output video 25 is similar to the input video 24.
[0026]
In this way, the image analysis inclination angle calculation unit 53 first obtains the vertical difference pixel 86 and the horizontal difference pixel number 87, and generates the inclination angle using the difference pixel number when the difference pixel number is equal to or larger than the predetermined pixel number. If the difference pixel number is equal to or smaller than the predetermined pixel number, the inclination angle is generated by obtaining the dot interval of the lowest and highest luminance of the dot line or the ratio of the luminance value at one end to the luminance value of the white line. Accordingly, an accurate and precise tilt angle can be generated regardless of whether the tilt angle between the vertical plane with respect to the projection optical axis 26 and the projection plane 70 is large or small.
[0027]
【The invention's effect】
As described above, according to the present invention, the vertical and horizontal tilt angles between the projection optical axis and the projection surface of the projection apparatus can be calculated easily and accurately. By doing so, there is an effect that the image projected on the projection surface can be accurately corrected to a correct state.
[0028]
This is because white and black straight lines are alternately arranged at intervals of 1 dot from the projection lens of the projection device arranged in the horizontal direction and the vertical direction from the imaging lens of the digital camera of the tilt angle measurement device. When projecting a test pattern consisting of a vertical and horizontal direction onto the projection surface and the difference in the number of pixels at both ends of the test pattern captured by the digital camera is greater than or equal to a predetermined number of pixels Generate the tilt angle using the difference pixel number, and if the difference pixel number is less than or equal to the predetermined pixel number, obtain the ratio of the dot interval of the lowest and highest luminance of the dot line or the luminance value of the white line to the luminance value of the white line By generating the tilt angle, the vertical and horizontal tilt angles between the projection optical axis and the projection surface of the projection device can be accurately calculated. Because it can be controlled to eliminate the distortion of the screen.
[Brief description of the drawings]
FIG. 1 is a schematic block configuration diagram of a projector having an inclination angle measuring device according to an embodiment of the invention.
FIG. 2 is a schematic explanatory view of a projector having the tilt angle measuring apparatus of the present invention.
(A) is a typical side view which shows a projection state.
FIG. 2B is a schematic front view of the projector.
(C) is a schematic diagram of the imaging screen of a digital camera.
FIG. 3 is a schematic diagram of a test pattern projected from a projection device onto a projection surface in an inclination angle measurement mode.
(A) is a vertical line test pattern.
(B) is a horizontal line test pattern.
FIG. 4 is a schematic flowchart showing a standard process for correcting an output image of a liquid crystal display unit from a difference pixel number.
FIG. 5 is a schematic diagram showing moiré appearing in a dot row when the direction of the dot row of the captured image and the direction of the test pattern are inclined by taking a horizontal line test pattern as an example.
(A) shows the case where the direction of a dot row and the direction of a test pattern correspond.
(B) shows a case where the direction of the dot row and the direction of the test pattern are inclined by 0.5 × dot interval at both ends of the dot row.
(C) shows a case where the direction of the dot row and the direction of the test pattern are inclined by 1.0 × dot interval at both ends of the dot row.
(D) shows a case where the direction of the dot row and the direction of the test pattern are inclined by 1.5 × dot interval at both ends of the dot row.
FIG. 6 is a schematic diagram showing moiré appearing in a dot row when the direction of the dot row of the captured image and the direction of the test pattern are inclined by taking a horizontal line test pattern as an example.
(E) shows a case where the direction of the dot row and the direction of the test pattern are inclined by 2.0 × dot interval at both ends of the dot row.
(F) shows a case where the direction of the dot row and the direction of the test pattern are inclined by 2.5 × dot interval at both ends of the dot row.
(G) shows a case where the direction of the dot row and the direction of the test pattern are inclined by 3.0 × dot interval at both ends of the dot row.
FIG. 7 is a schematic flowchart showing a standard process for correcting an output image of a liquid crystal display unit from the brightness value at the dot interval and the end of the lowest and highest luminances.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Projector 20 Projection apparatus 21 Projection lens 22 Liquid crystal display part 23 Image control part 24 Input image 25 Output image 26 Projection optical axis 30 Inclination angle measuring apparatus 40 Test pattern generation apparatus 50 Digital camera 51 Imaging lens 52 Imaging element 53 Image analysis inclination angle Calculation unit 60 CPU
70 Projection surface 80 Imaging screen 83a Vertical line test pattern 83b Horizontal line test pattern 86 Vertical difference pixel number 87 Horizontal difference pixel number 90 Placement table 96 Vertical luminance change 97 Horizontal luminance change S11 to S14, S21 to S24 Steps

Claims (7)

A tilt angle measuring device that calculates the tilt angle between the projection optical axis of the projector and the projection surface of the projector, and controls the output image of the image display unit according to the calculated tilt angle, thereby correcting the distortion of the image on the projection surface. A projector to correct,
The tilt angle measuring device includes a test pattern generation device, a digital camera, and an image analysis tilt angle calculation unit,
The imaging lens of the digital camera is provided on the irradiation side surface of the projector at predetermined intervals in the vertical direction and the horizontal direction from the projection lens of the projection device,
In the tilt angle calculation mode, the projection device projects a test pattern in the vertical direction and the horizontal direction with respect to the projection surface so as to form an image near the edge of the imaging screen of the digital camera. It is composed of a plurality of white and black straight lines alternately arranged at intervals of 1 dot of the image sensor of the digital camera,
The image analysis inclination angle calculation unit calculates the inclination of the test pattern on the projection surface captured by the digital camera, and if the inclination is equal to or greater than a predetermined angle, the number of pixels at the intersection of the test pattern and both ends of the imaging screen. When the inclination is equal to or smaller than a predetermined angle, the state of change on the dod line of the luminance of the moire generated on the dod line is obtained by the intersection angle between the test pattern and the dod line, An inclination angle between the test pattern and a reference line indicating a vertical direction and a horizontal direction of the projection apparatus is analyzed from a difference in the number of pixels and a change in luminance, and the projection of the projection apparatus of the projector is calculated from the inclination angle. A projector having an inclination angle measuring device for calculating an inclination angle between an optical axis and the projection surface. The projector having an inclination angle measuring device according to claim 1, wherein the image sensor of the digital camera is an image sensor having a resolution of 640 × 480 dots VGA (video graphic array). The analysis of the inclination angle between the test pattern imaged by the digital camera and the reference line from the imaging screen of the imaging device of the digital camera is performed at the intersection of the test pattern and both ends of the imaging screen. The inclination angle measuring device according to claim 1 or 2, wherein the difference pixel number between the corresponding two dots is calculated, and the inclination angle is calculated by a table in which the difference pixel number and the inclination angle that are created in advance are associated with each other. Projector. The test pattern and a reference line indicating the vertical direction and the horizontal direction of the projection device from the change on the dod line of the brightness of the moire generated on the dod line according to the intersection angle between the test pattern and the dod line In the analysis of the inclination angle, when one end of the black line of the test pattern is matched with one end of the dodd line, when there is a peak of the upper limit of the luminance value on the dod line, the total number of dots of the dod line Is obtained by dividing the value by the number of dots between the center of the upper limit peak and the one end to make the number of dots the difference pixel number between the two ends of the imaging screen of the test pattern, and the luminance on the dot line When there is no upper limit peak of the value, the value obtained by dividing the luminance value at the end opposite to the one end by the luminance value corresponding to the white line is the number of dots. The tilt angle measuring device according to claim 1, wherein the tilt angle is calculated by a table in which the difference pixel number created in advance and the tilt angle are associated with each other, assuming that there is a difference pixel number between both ends of the imaging screen. Projector. Control of the output video of the video display unit according to the tilt angle between the projection optical axis of the projection device of the projector and the projection surface is an input of the video display unit that is calculated in advance corresponding to the tilt angle. The projector having the tilt angle measuring device according to claim 1, which is executed by creating an LSI control parameter based on a correction value of an image and controlling an image processing LSI for a projector. The projector having the tilt angle measuring device according to claim 1, wherein the projector is a liquid crystal projector. The projector having a tilt angle measuring device according to claim 1, wherein the projector is a DLP (Digital Light Processing) projector.

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