JP3716265B2 - Method for detecting zoom state of projector and projector - Google Patents

Description

  The present invention relates to a projector, and to a zoom state detection method for a projector.

  In recent years, with the development of liquid crystal technology and DMD (Digital Micromirror Device, DMD is a registered trademark), projectors have become smaller and have higher performance, and are being used not only in offices but also in schools and homes.

  However, unlike a display-type television, a projector projects an image on a screen or a wall in front of the projector, so that there is a problem that the image is distorted depending on the state of the screen or wall, the installation posture of the projector, and the like.

  A mechanism for generating such image distortion will be described with reference to FIG. FIG. 6A shows a projection situation when the optical axis of the projection lens 102 of the projector 101 is set in a direction perpendicular to the screen 4. The heights a1 and b1 of the image in the vertical direction of the optical axis (indicated by the chain line in the figure) are equal and are projected in the same direction in the vertical direction. In this state, a predetermined image is accurately projected without distortion (in the following description, an image projected on a screen by a projection lens is referred to as a projected image). However, the projector is not always set in such a positional relationship with respect to the screen. Due to restrictions on the projection location and the position of the screen, the projector is set upward as shown in FIG. 6B, for example. In some cases, it must be done. At this time, the height a2 of the projection image above the optical axis is larger than the height b2 below, and a projection image distorted in the vertical direction is generated. A similar problem also occurs when the projector 101 is projected obliquely from the right or left side with respect to the screen 4. In this case, if FIG. 6 is considered as a plan view of the projector, that is, a view of the projector from above, it is understood that in FIG. 6B, the left side of the optical axis as viewed from the projector is enlarged and projected. I can do it.

  Such a distortion of the projected image is actually referred to as trapezoidal distortion because an image that should originally be projected as a rectangle is projected in a trapezoidal shape, and a technique for correcting the trapezoidal distortion is referred to as trapezoidal correction. Many techniques for keystone correction have been disclosed so far. For example, a method for adjusting the angle of the liquid crystal display unit based on the detection results of both detection means, including a detection means for the installation angle of the liquid crystal projector and a distance detection means for detecting the distance between the projector and the screen. (For example, refer to Patent Document 1).

  By the way, the projector is usually provided with a zoom function, and can project an image in a wide mode for projecting a large image, a tele mode for projecting a small image, and any state therebetween. However, the distortion of the projected video changes depending on the difference in zoom state. With reference to FIG. 7, the influence of the difference in zoom state on the projected image will be described. In the drawing, projection is performed at the projection angle θw in the wide mode, and projection is performed at the projection angle θT in the tele mode. In the wide mode, the screen 4 projects an image with a height a3 above the optical axis and a video with a height b3 below. In the tele mode, an image having a height c3 is projected above the optical axis and an image having a height d3 is projected below the screen 4. However, the ratio of a3: b3 and the ratio of c3: d3 are different, and the distortion of the projected video is further enlarged in the zoom state. Therefore, in a projector with a zoom function, it is necessary to adjust image correction depending on the zoom state.

  To that end, it is apparent that a means for detecting the zoom state of the projector is necessary. Furthermore, the detection of the zoom state is indispensable not only when correcting the keystone, but also when storing the zoom state or when returning to a certain zoom state.

As a detecting means of the zoom means, a gear is provided on the zoom ring, a variable resistor is moved through the gear to detect the position of the zoom ring, and a lens group constituting the projection lens is an optical axis. A number of methods for detecting the amount of rotation of the cam mechanism for moving in the direction with a potentiometer, rotary switch, rotary encoder, optical position detection mechanism, etc., and a method for arranging a large number of position detection electrodes in the direction of the lens barrel are disclosed. (For example, refer to Patent Documents 2 to 4.)
Japanese Patent Laid-Open No. 9-281597 JP 2002-90880 A JP 2003-143620 A JP 2003-131323 A

  However, these zoom state detection mechanisms have to be provided with dedicated parts and devices, regardless of what method is adopted. In recent years, projectors have been used for home use and the like, and there has been a strong demand for further cost reduction. Conventional techniques that require such a dedicated detection mechanism have limited cost reduction.

  In view of the above situation, an object of the present invention is to provide a zoom state detection method and a projector that do not require a dedicated detection mechanism and can reduce costs.

  According to a method of detecting a zoom state of a projection lens of a projector according to the present invention, a step of projecting a predetermined reference pattern from a projection lens and displaying a projected image of the reference pattern on a projection surface, and a projection image displayed on the projection surface There are steps of obtaining a projected video image by imaging, obtaining a size occupied by the reference pattern in the projected video image, and calculating a zoom state of the projection lens based on the size.

  In recent projectors, an image pickup device is usually mounted for an autofocus function or the like, and since a projected image can be picked up by this image pickup device, no new parts are required and it has been used in the past. A mechanism for detecting the zoom state is also unnecessary. Therefore, a zoom detection function equivalent to that of a conventional projector can be obtained only by adding new software, and the cost can be reduced by reducing the number of parts.

  Here, the reference pattern can be two points separated by a predetermined distance.

  The projected video image may be picked up by an image pickup device in which a large number of photoelectric elements are arranged, and the size may be obtained based on the position where the photoelectric elements in which the reference pattern is picked up are arranged.

  Further, the size may be obtained as a ratio of the interval between the photoelectric elements in which two predetermined portions of the reference pattern are recorded and the interval between the predetermined photoelectric elements of a large number of imaging elements.

  The reference pattern can be obtained by driving or not driving only the predetermined light modulation element of the light modulation device in which a large number of light modulation elements are arranged.

  A method for detecting a zoom state of a projection lens of a projector according to the present invention includes a step of creating in advance a table indicating a correspondence relationship between a size, an angle between an optical axis of the projection lens and a normal of a projection surface, and a zoom state; The method may further include a step of detecting an angle and a step of calculating a zoom state by comparing the size and the angle with a table.

  The projector according to the present invention includes a projection lens that projects a predetermined reference pattern, an imaging device that captures a projected image of the reference pattern displayed on the projection surface to obtain a projected image, and the reference pattern occupies the projected image. An image control unit that calculates a size and calculates a zoom state of the projection lens based on the size.

  The imaging device may have a large number of arranged photoelectric elements, and the image control unit may be configured to obtain a size based on the arranged positions of the photoelectric elements on which the reference pattern is recorded.

  Furthermore, the projector of the present invention stores in advance a tilt angle output device that detects the angle between the optical axis of the projection lens and the normal of the projection surface, and a table that indicates the correspondence between the size, the angle, and the zoom state. The image control unit can be configured to calculate the zoom state by comparing the size and the angle detected by the tilt angle output device with a table.

  As described above, the zoom state detection method for a projector according to the present invention and the projector capture an image of a reference pattern using an already installed image sensor, and analyze the data to capture the zoom state of the projection lens. Can be detected. For this reason, a conventionally used mechanism for detecting the zoom state is not required, and an equivalent function can be obtained only by adding new software. Therefore, the number of parts is reduced and costs are reduced, and the function of the deleted parts is replaced with software, so that the possibility of electrical and mechanical malfunctions is reduced, and the reliability of the projector is improved. You can also.

  Details of the projector of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a projector according to the present invention. The projector 1 includes a projection lens 2 having a zoom adjustment mechanism, an image display unit 11 having a light modulation device and a light combining prism, an image control unit 12 for controlling the light modulation function of the image display unit 11, and operations of the entire projector. A central processing unit 13 to be controlled and an inclination angle output device 14 for detecting and outputting the horizontal and vertical angles between the optical axis of the projection lens 2 and the normal of the screen 4 in front are provided. The projector 1 also includes a zoom manual adjuster 21 that manually performs zoom adjustment of the projection lens 2 and an image sensor 3 that captures a projected image.

  The image display unit 11 includes a light source, a color separation optical system that splits light emitted from the light source into red (R), green (G), and blue (B) colors, a liquid crystal panel (not shown), and a DMD. And a light modulating unit that modulates the dispersed light in accordance with an input signal, and a color combining prism (not shown) that combines the modulated light.

  An imaging element 3 is provided on the surface provided with the projection lens 2 to capture a projected image projected on the front screen 4 constituting the projection surface and obtain a projected video image. The image sensor 3 is configured by, for example, a CCD (Charge Coupled Device) device. CCD devices generally have hundreds of thousands to millions of photodiodes arranged in a grid, and signal charges accumulated in the photodiodes upon receiving light are photoelectrically transferred vertically adjacent to the photodiodes. The data is sequentially transferred to the output circuit via the CCD or the horizontal transfer CCD, and the amount of light received by each of the lattice-shaped photodiodes is obtained as a one-dimensional signal. The CCD device is an example, and other devices may be used as long as it can capture a projected image.

  The tilt angle output device 14 outputs an output value corresponding to the tilt angle in the vertical direction and / or horizontal direction of the normal line of the screen 4 and the optical axis of the projector 1 to the image control unit 12. Manual output, automatic output, or a combination thereof may be used. A conventional technique can be used as the method of automatically detecting the tilt angle. For example, a method using a gravity sensor is disclosed in Japanese Patent Application Laid-Open No. 2003-5278. In addition, for the horizontal inclination, a method of accurately measuring using a laser pointer and a digital camera having an image sensor, or projecting light from a plurality of light emitting elements through a single light projecting lens, The reflected light is received by a plurality of light receiving elements through one light receiving lens, and a tilt angle is obtained by using the light receiving position and light intensity, or uniform luminance light is projected from a projection lens of a projection device onto a screen, It is possible to use a method in which reflected light from the screen is received by a light receiving element via a single light guide, and an inclination angle is obtained using the light receiving position and light intensity.

  FIG. 2 is a schematic diagram showing the relationship between the reference pattern and the projected video image by the image sensor. 2A, 2B and 2C are plan views of the projector 1 as viewed from above, and the diagrams on the right side are AA and B- It is a cross-sectional arrow view shown by B and CC.

  2A, 2 </ b> B, and 2 </ b> C, the projector 1 is installed facing the screen 4 on which an image is projected. A projection lens 2 and an image sensor 3 are provided on the surface of the projector 1 that faces the screen 4.

  In FIG. 2A, the projector 1 is set to the wide mode, and the projection lens 2 projects at the projection angle θw. The projection lens 2 and the screen 4 are separated by a distance L1. The zoom state can be manually adjusted with the zoom manual adjuster 21, and may be adjusted as appropriate from an interface unit (not shown) provided on the main body of the projector 1.

  The projection lens 2 projects predetermined reference patterns Ma and Na under the control of the image control unit 12 (details will be described later). Further, the image sensor 3 captures an image of the imaging angle θs.

  Here, the reference pattern will be described with reference to FIG. FIG. 3 is a plan view of the liquid crystal panel 16 including the liquid crystal elements 17 arranged in a 30 × 20 matrix. Of course, the actual number of liquid crystal elements 17 is not limited to this. In FIG. 3, among the liquid crystal elements 17, only the liquid crystal element M located at (10 rows, 10 columns) and the liquid crystal element N located at (10 rows, 20 columns) are driven, and the others are not driven. . When the liquid crystal panel 16 is driven with such a reference pattern composed of two points separated by a predetermined distance, as shown in the right figure of FIG. Ma and Na are displayed.

  2A is a cross-sectional view taken along line AA in FIG. 2A, and shows a display state of the bright spots Ma and Na on the screen 4 in a plan view. A frame indicated by a broken line is a range of a projected image, and has a width B1 on the screen 4. In the projected image, two bright spots Ma and Na appear at positions corresponding to the liquid crystal elements M and N shown in FIG. 3, and are displayed on the screen 4 at a distance A1 from each other. The imaging device 3 captures a certain range of the screen 4 including the projected video as a projected video image, and the range of the width C1 in the screen 4 is the imaging range.

  Next, the situation when the distance between the projection lens 2 and the screen 4 is changed (separated) to the distance L2 while the zoom state is maintained in the wide mode will be described. In FIG. 2B, a frame indicated by a broken line is a range of a projected image, and has a width B2 on the screen 4. Two bright spots Mb and Nb appear at positions corresponding to the liquid crystal elements M and N in the projected image, and are displayed on the screen 4 at a distance A2 from each other. Further, the range of the width C <b> 2 of the screen 4 is the imaging range of the imaging device 3.

  2A and 2B, when the distance between the projection lens 2 and the screen 4 is increased, the distance A2, the width B2, and the width C2 are larger than the distance A1, the width B1, and the width C1, respectively. It has become. However, since both FIGS. 2A and 2B are in the wide mode, the projection angle θw is the same, and the imaging angle θs of the imaging device 3 is also the same, so the ratio of A1: B1: C1 and A2: The ratio of B2: C2 is constant at the ratio L2 / L1.

  Next, the situation when the zoom state is changed to the tele mode while maintaining the distance L2 between the projection lens 2 and the screen 4 will be described with reference to FIG. The explanation in the figure is the same as (a) and (b). A frame indicated by a broken line is a range of a projected image, and has a width B3 on the screen 4. Two bright spots Mc and Nc appear at positions corresponding to the liquid crystal elements M and N in the projected image, and are displayed on the screen 4 at a distance A3 from each other. Further, the range of the width C <b> 3 in the screen 4 is the imaging range of the imaging device 3.

  Here, comparing FIGS. 2B and 2C, the distance between the projection lens 2 and the screen 4 is the same, but the zoom state is different, and the projection angle θw is reduced to the projection angle θT. Yes. Accordingly, in the display on the screen 4, the interval A3 is smaller than the interval A2, and the width B3 is also smaller than the width B2. However, the ratio of A2: B2 and A3: B3 is constant because it depends only on the positional relationship between the liquid crystal elements M and N. On the other hand, since the imaging angle θs of the imaging device 3 is constant and the distance between the projection lens 2 (that is, the imaging device 3) and the screen 4 is also constant, the width C3 is the same as the width C2. From the above, the ratio of A2: C2 (or B2: C2) and the ratio of A3: C3 (or B3: C3) are different.

  From the above, if the zoom state is the same, the ratio of the interval A and the width C is constant regardless of the distance between the projection lens 2 and the screen 4, and if the zoom state is different, the ratio of the interval A and the width C is different. . Therefore, the zoom state can be detected by analyzing these ratios. The above is the basic principle of zoom state detection using an image sensor and a reference pattern. In addition, although it demonstrated as what projects a bright spot here, it is not necessary to be a bright spot if the reference point which can be distinguished from the circumference | surroundings can be provided when the image pick-up image 3 is imaged. For example, a black spot may be projected instead of a bright spot. Since the screen 4 and the wall are usually white or light in color, if a black dot is projected, the luminance is reduced accordingly, and can be used as a reference point in the same manner. Further, a cross-shaped reference pattern in which vertical and horizontal lines intersect may be used instead of the points, and the position of the intersection can be determined more accurately by recognizing the vertical and horizontal lines.

  FIG. 4 shows a processing flow for zoom state detection. Hereinafter, a specific zoom state detection method will be described in detail with reference to FIG.

  First, the projector 1 is turned on (step 51), or a trapezoidal correction start command is input from the interface unit (step 51 '). When the projector 1 and the screen 4 are fixed and trapezoid correction is not necessary, the projector 1 may be set in advance so that the following processing is not started even when the projector 1 is turned on.

  Next, the projector 1 projects the reference pattern on the screen 4. As a result, two bright spots Md and Nd separated from each other are displayed on the screen 4 (step 52).

  Next, the screen 4 on which the bright points Md and Nd are displayed is imaged by the image sensor 3 (step 53).

  Next, the image sensor 3 acquires the interval A between the bright spots Md and Nd. Hereinafter, a description will be given with reference to FIG. FIG. 5 shows the arrangement of photodiodes in a CCD device. The photo diode auto 31 corresponding to the number of pixels is arranged in the CCD device. For example, in the case of the CCD device of the horizontal pixel 400 and the vertical pixel 480, a total of 192000 from the address (1, 1) to the address (400, 480). A number of Photo Dai Autos 31 are arranged. These photo die autos 31 output signals according to the amount of received light. These photodiodes 31 usually have a substantially concentric luminance distribution centered on the photodiode 31 that captures the vicinity of the bright spots Md and Nd, so that the photodiode corresponding to the maximum luminance is obtained by obtaining the center of the concentric circle. 31 addresses can be acquired. Since there are two such addresses corresponding to the bright spots Md and Nd (in FIG. 5, the bright spot Nd is omitted), the interval A is the distance (the bit) separation distance (or bit) of the photodiode 31 corresponding to the maximum luminance. The number of elements between two bright spots). Since the C value is equal to the number of horizontal pixels, C = 400 in the above case. From the above, the A / C value can be obtained. The A / C value may be a ratio between the interval between the pixels where the two predetermined portions of the reference pattern are recorded and the interval between the predetermined pixels of a large number of pixels. A separation distance between any two pixels other than the number of horizontal pixels may be used.

  Thus, the A / C value is an index indicating the size that the reference pattern occupies in the projected video image. When the A / C value is stored at the factory, for example, how many bits the distance between the reference patterns is in a projected video image in which the reference pattern is projected in the wide mode, the zoom state is obtained based on the wide mode. You can also.

  In parallel with this, the projector 1 acquires the tilt angle according to the above-described method (step 55).

  Next, the zoom state is obtained from the obtained A / C value and the tilt angle. Specifically, a zoom amount table corresponding to the A / C value and the tilt angle is prepared in advance, and the zoom amount can be easily obtained by referring to this table.

  Then, keystone correction is performed based on the calculated zoom amount (step 57), and when the keystone correction is completed, it becomes possible to project predetermined image data.

  As described above, according to the projector of the present invention, the zoom state of the projection lens can be performed by the image sensor and software processing, and the image sensor is already equipped in a conventional projector for the purpose of autofocusing or the like. In general, no new mechanism is required. In addition, mechanisms such as gears and variable resistors that have been conventionally required are not required. As a result, the number of parts of the projector can be reduced, and the cost can be reduced while maintaining the same function as the conventional one. Further, the possibility of occurrence of electrical / mechanical problems is reduced, and the reliability of the projector can be improved.

It is a schematic diagram which shows the relationship between the image projected on the screen and the imaging screen of the projector by the 1st Embodiment of this invention. It is a schematic diagram which shows the relationship between a projection image and the imaging range by an image pick-up element. It is explanatory drawing of a reference | standard pattern. It is a processing flow figure of zoom state detection. 2 shows an arrangement of photodiodes of a CCD device. It is a side view of the projector of a prior art. It is a figure explaining the influence which the difference in the zoom state in a prior art has on a projection image | video.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Projector 11 Image display part 12 Image control part 13 Central processing unit 14 Inclination angle output device 16 Liquid crystal panel 17 Liquid crystal element 2 Projection lens 21 Zoom manual adjuster 3 Image pick-up element 31 Photodai auto 4 Screen

Claims (9)

Projecting a predetermined reference pattern from the projection lens and displaying a projected image of the reference pattern on the projection surface;
Capturing the projected video displayed on the projection surface to obtain a projected video image;
Obtaining a size occupied by the reference pattern in the projected video image;
Calculating a zoom state of the projection lens based on the size.   The zoom state detection method according to claim 1, wherein the reference pattern is two points separated by a predetermined distance. The projected video image is captured by an image sensor in which a large number of photoelectric elements are arranged,
The zoom state detection method according to claim 1, wherein the size is obtained based on a position where the photoelectric elements in which the reference pattern is imaged are arranged.   The size is obtained as a ratio of an interval between the photoelectric elements in which two predetermined portions of the reference pattern are recorded and an interval between the predetermined photoelectric elements of the multiple imaging elements. The zoom state detection method described.   5. The method according to claim 1, further comprising: driving the predetermined light modulation element of a light modulation device in which a large number of light modulation elements are arranged, or obtaining the reference pattern without driving the light modulation element. The zoom state detection method described. Creating in advance a table indicating the correspondence between the size, the angle between the optical axis of the projection lens and the normal of the projection surface, and the zoom state;
Detecting the angle;
The zoom state detection method according to claim 1, further comprising a step of calculating the zoom state by comparing the size and the angle with the table. A projection lens that projects a predetermined reference pattern;
An image sensor that captures a projected image of the reference pattern displayed on the projection surface to obtain a projected image; and
A projector having an image control unit that calculates a size occupied by the reference pattern in the projection video image and calculates a zoom state of the projection lens based on the size; The image sensor has a large number of photoelectric elements arranged,
The projector according to claim 7, wherein the image control unit obtains the size based on a position where the photoelectric elements on which the reference pattern is recorded are arranged. An inclination angle output device for detecting an angle between an optical axis of the projection lens and a normal line of the projection surface;
A storage unit that stores in advance a table indicating a correspondence relationship between the size, the angle, and the zoom state;
The projector according to claim 8, wherein the image control unit calculates the zoom state by comparing the size and the angle detected by the tilt angle output device with the table.

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