JP2009238167A - Position detection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position detection apparatus of a digitizer capable of preventing detection of a virtual image by an image sensor by preventing reflection of an input screen being a display screen. <P>SOLUTION: The position detection apparatus is composed by having a plurality of image sensors 102, 103 equipped in a side and a top part of the input screen of the digitizer, light sources arranged in neighborhoods of the image sensors and irradiating light along the input screen of the digitizer so as to cover a whole face of the input screen, a reflection tape having retroreflectivity perpendicularly arranged on the input screen, and a control means 104 for carrying out image processing using image signals imaged by the image sensors as input and calculating coordinates of an indicated position on the input screen indicated by an input means. Antireflection processing is applied on the input screen of the digitizer. A cover 401 is provided so as to cover the image sensors, the light sources, and the control means, and antireflection processing is applied to a rear face of the cover. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a position detection device, and more particularly, to a position detection device that detects a designated coordinate position on an input surface of a coordinate input device.

  In recent years, the use of an electronic whiteboard (Interactive White Board, hereinafter simply referred to as IWB) has been increasing. IWB uses PDPs, LCDs, projectors, etc., which are used as general display devices, and it uses input means such as fingers and electronic pens to write letters, figures, etc. on the blackboard as if they were chalk on the blackboard. The position detection device provided for detecting the coordinate position of the input means described above is realized by detecting the coordinate position on the display screen of the input means and projecting the detection result to the display device. Yes. In addition, tablets, touch panels, and the like are prevalent as conventional techniques related to a coordinate input device using a position detection device.

  As a method for realizing the position detection apparatus as described above, various techniques such as an electromagnetic induction method and an ultrasonic method have been put into practical use. Furthermore, in recent years, position detection devices that detect the position of an input means such as a finger or an electronic pen by using a technique for performing image processing on image data acquired by an image sensor are becoming widespread, and drawing responsiveness is increasing. The number of uses is increasing year by year due to the advantages of good resistance to external noise such as infrared rays, sunlight, and temperature changes.

  A position detection device using an image sensor is configured by attaching an image sensor around the input surface in order to detect the position of the input means such as a finger or an electronic pen on the input surface of the coordinate input device. It is common. The position detection device includes at least two image sensors and a control board as a control device that processes an image acquired by the sensor. When two or more image sensors are installed, the position of the input means on the input surface is detected from a plurality of visual field positions, and the control device processes the image data acquired by the plurality of image sensors, and performs trigonometry Is used to calculate the position of the input means.

  In addition, the above-described position detection device is configured by installing a plurality of light sources that emit light such as LEDs in the vicinity of the image sensor. The light from this LED needs to be irradiated so as to cover the entire input surface along the input surface without being directly irradiated to the input surface. And the light from such LED irradiates the retroreflection tape installed in the frame installed so that the circumference | surroundings of the input surface may be surrounded. The reflective tape uses a retroreflective material such as a corner cube reflector, and the light emitted from the LED is retroreflected in the same direction as incident on the retroreflective tape. The image sensor receives the reflected light and captures an image.

  As described above, an environment for irradiating light on the surface of the input surface is created, and the pointing object, which is an input means such as a finger or an electronic pen, approaches the input surface to block the light. A shadow is detected. The shadow position is acquired as an image by a plurality of image sensors, and the control device calculates the position coordinates of the input means.

  The image sensors and control boards that make up the position detection device described above are designed to ensure safety and quality, such as avoiding electric shock accidents caused by users touching board circuits and mounting cables, and physical damage to them. It cannot be exposed to the outside from the viewpoint. In addition, these image sensors and control boards are exposed and easily affected by the surrounding environment. For example, they are exposed to external dust, unnecessary radiation generated from the board circuit, and the surrounding environment. There is a high possibility that an operation problem will be caused by the influence of noise. For this reason, these image sensors, boards, cables, etc. are dealt with so that they are not easily touched by the user and the influence from the surrounding environment is reduced by installing a cover to isolate them from the outside. Yes.

For example, the techniques described in Patent Documents 1 and 2 are known as conventional techniques related to a position detection apparatus using an image sensor used in the coordinate input apparatus as described above.
Japanese Patent No. 3931030 Japanese Patent No. 3986710

  In the above-described position detection device according to the prior art, the light reflected by the reflective tape is normally reflected in the same direction as the incident direction. As the light source, a directional LED or the like is used, but the luminous flux usually has a spread of several to several tens of degrees. For this reason, the light reflected by the reflecting tape is reflected as reflected light in a direction that does not exactly coincide with the incident direction, which is one of the causes of optical axis misalignment. In addition, the direction of retroreflected light may deviate from the direction of input light due to distortion and tilt of the reflective tape mounting part due to distortion of the entire coordinate input device, foreign matter and dirt on the reflective tape, etc. The direction of retroreflected light may also be deviated from the direction of input light due to the deviation of the optical axis of the installation part.

  For the reasons described above, the position detection device according to the prior art is such that the position of the light incident on the image sensor is shifted from the position of the normal reflected light because a part of the light is reflected by the input surface or the like. When the pointing object as the input means is placed in the area where the light deviation occurs, the image sensor will detect the shadow of one of the real image and the virtual image, or both input means. It is difficult to capture the position and size of the original object, which causes problems such as coordinate shift and malfunction.

  The object of the present invention is to solve the problems of the prior art as described above, prevent reflection of light on the input surface of the coordinate input device, and prevent the image sensor from detecting a virtual image. It is to provide a detection device.

  According to the present invention, the object is to provide a position detection device for detecting the position of an input means that is a pointing object located on the input surface of the coordinate input device, on the side, above or below the input surface of the coordinate input device. A plurality of image sensors provided in at least two positions; a light source that is installed in the vicinity of the image sensor and that irradiates light so as to cover the entire input surface along the input surface of the coordinate input device; Image processing is performed using a retroreflective reflective tape placed at right angles to the input surface so as to surround the input surface of the coordinate input device and an image signal captured by the image sensor, and the input unit instructs And a control means for calculating the coordinates of the indicated position on the input surface, and this is achieved by applying antireflection processing to the input surface of the coordinate input device.

  By applying anti-reflective processing to the input surface of the coordinate input device, it is possible to prevent or reduce the generation of virtual images captured by the image sensor, thereby displaying detection positions with high drawing accuracy and few malfunctions. It is possible.

  Embodiments of a position detection device according to the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a coordinate input device using a position detection device according to an embodiment of the present invention.

  The coordinate input device shown in FIG. 1 is a display surface on which an image or the like is displayed and is an input surface of the coordinate input device, and a display control device 106 such as a projector that displays the image or the like on the screen 101. The image information from the pointing object 105 as an input means for pointing on the screen 101 and the two image sensors 102 and 103 and the image sensors 102 and 103 constituting the position detection device 100 according to the embodiment of the present invention is processed. The control board 104 having a control means for calculating the coordinate position of the pointing object 105 on the screen and the information on the coordinate position on the screen of the pointing object 105 calculated by the control means on the control board 104 are received and received as position information. A process for displaying the position information on the screen 101 is performed and the display control device 106 is used. Is constituted by an arithmetic unit 107 according to a PC or the like to display the locus of movement of the screen 101 instructs the object 105 on the like. Although not shown in FIG. 1, a light source such as an LED is provided in the vicinity of the image sensors 102 and 103, and is retroreflective installed at a right angle to the surface of the screen 101 so as to surround the screen 101. Reflective tape is provided.

  In the above description, the image sensors 102 and 103 use a light receiving element such as a CCD or a CMOS to acquire an image through an imaging lens, and the structure thereof may be the same as that known as a so-called digital camera. . The pointing object 105 as an input means may be a finger, a stick, or the like, or an electronic pen or the like that has a communication function using infrared rays or the like and has an additional function linked to the control means on the control board 104. There may be. Further, instead of the screen 101 serving as the input surface of the coordinate input device and the display control device 106 such as a projector, a display screen such as a PDP or LCD can be used.

  In the example shown in FIG. 1, the image sensors 102 and 103 are installed at the left and right corners of the upper part of the screen 101, and the control board 104 having the control means is installed at the approximate center of the upper part of the screen 101. For example, the image sensors 102 and 103 may be installed at the left and right corners of the lower part of the screen 101, and the control board 104 having the control means may be installed at the approximate center of the lower part of the screen 101.

  FIG. 2 is a diagram for explaining an attached state of the image sensor, the light source, and the reflective tape.

  As shown in FIG. 2 (a), retroreflective light reflecting tapes 201 are installed on the left and right sides and the lower end of the screen 101, which are input surfaces of the coordinate input device, so as to be perpendicular to the screen 101. 203 is provided. The reflective tapes 201 to 203 are configured using a reflective material having retroreflectivity such as a corner cube reflector. Further, as shown in FIG. 2B, the image sensor 102 (103) is directed so that the light receiving surface 205 can receive reflected light from the reflective tape, and the image sensor on the left side of the screen. 102 receives the reflected light from the right and lower reflective tapes 202 and 203 of the screen 101, and the image sensor 103 on the right side of the screen receives the reflected light from the left and lower reflective tapes 201 and 203 of the screen 101. And is supposed to take an image.

  In the vicinity of the image sensor 102 (103), in the embodiment of the present invention, a plurality of light sources 204 by light emitting elements such as LEDs are installed on the image sensor. The light from the light source 204 is emitted along the surface of the screen 101 serving as the input surface of the coordinate input device so as to cover the entire screen 101 and irradiates the reflective tapes 201 to 203. The light emitted from the light source 204 is reflected on the reflective tape in the same direction as the incident direction, and the reflected light is received by the image sensor 102 (103), and the reflective tape is imaged.

  In the above description, when the input unit 105 that is the pointing object is on the surface of the screen 101, the input image that is the pointing object on the screen 101 is input to the captured image that is captured when the reflected light is input to the image sensor 102 (103). When the means approaches and blocks the light beam, a shadow is detected on the image sensor, and the input means 105 is copied as a shadow on the reflective tape. The control means on the control board 104 is coordinates indicating the position on the input surface of the screen 101 where the input means 105 is located from the position of the shadow on the reflection tape of the image as described above picked up by the two image sensors. The position (X, Y) is calculated.

  In order to improve the accuracy of the calculated coordinate position, it is necessary to match the optical axis of the image sensor with the optical axis from the light source. The method is described in detail in the above-mentioned Patent Documents 1 and 2, etc. In the embodiment of the present invention, those methods will be used.

  FIG. 3 is a diagram for explaining the outline of the position detection method based on the angle of view of the image sensor and an example of a captured image.

  FIG. 3A shows the angle of view of the image sensor. The image sensor 103 provided on the upper right side of the screen 101 is located near the uppermost part of the reflective tape 201 provided on the left side of the screen 101 to the left of the lowermost part. The angle of view covers the entire area of the reflective tape 201 to the corner and the reflective tape 203 provided at the lower part of the screen 101 from the left corner to the lowermost part of the reflective tape 201 provided on the right side of the screen 101. is doing. The image sensor 102 provided on the upper left side of the screen 101 includes a reflective tape 202 from the vicinity of the uppermost portion of the reflective tape 202 provided on the right side of the screen 101 to the lower right corner, and the screen 101 from the right corner. It has an angle of view that covers the entire area with the reflective tape 203 provided at the lower part of the screen 101 up to the lowest part of the reflective tape 201 provided on the left side.

  Then, an image captured by the image sensor 103 provided on the upper right side of the screen 101 includes a reflective tape 203 provided at the lower part of the screen 101 and a left side of the screen 101 as illustrated in FIG. The reflection tape 201 provided on the camera is photographed. In the image of this example, the shadow of the input means 105 as the pointing object is imprinted on the screen of the reflective tape 203 provided at the lower part of the screen 101. Depending on the position of the input means 105, this shadow is imprinted on the screen of the reflective tape 201 provided on the left side of the screen 101.

  Further, an image captured by the image sensor 102 provided on the upper left portion of the screen 101 is a reflection tape 203 provided on the lower portion of the screen 101 as shown in FIG. The reflection tape 202 provided on the camera is photographed. In the image of this example, the shadow of the input means 105 as the pointing object is imprinted on the screen of the reflective tape 203 provided at the lower part of the screen 101. Depending on the position of the input means 105, this shadow is imprinted on the screen of the reflective tape 202 provided on the right side of the screen 101.

  The control means on the control board 104 has the input means 105 of the screen 101 from the position of the shadow on the reflection tape of the image as shown in FIGS. 3B and 3C captured by the two image sensors. A coordinate position (X, Y) indicating which position is on the surface is calculated. A known method can be used as a method for calculating the coordinate position.

  FIG. 4 is a diagram illustrating a schematic configuration of a cover of the position detection device. As described above, the image sensors 102 and 103 and the control board 104 constituting the position detection device are used to prevent an electric shock accident caused by a user touching a board circuit or a mounting cable, and to avoid physical damage thereof. It cannot be installed outside from the viewpoint of safety and quality assurance. Therefore, in the present invention, a cover that covers the image sensors 102 and 103 of the position detection device and the control board 104 is provided. Since this cover cannot place an object that does not transmit light within the range of the angle of view of the image sensors 102 and 103, it has a structure covering the other range.

  That is, the cover 401 according to the embodiment of the present invention is a long member whose cross section is configured in an L shape as shown in FIG. The cover 401 by this member is placed on the upper part of the screen 101 of the coordinate input device so as to cover the image sensors 102 and 103 and the control board 104 constituting the position detecting device 100 described above shown in FIG. It is attached. The cover 401 protects the image sensors 102 and 103 and the control board 104, and is installed for the purpose of reducing damage caused by external contact and noise reception / transmission. In particular, it is indispensable to use such a cover because there is a risk of electric shock if the periphery of the power source is exposed.

  FIG. 5 is a diagram for explaining generation of a virtual image when the light reflected by the reflective tape is detected by the image sensor after being reflected by the input surface. Here, description will be made assuming that imaging is performed by the image sensor 103 installed in the upper right corner of the screen 101.

  As described above, the light emitted from the light source installed in the vicinity of the image sensor 103 is radiated in any direction by the reflecting tapes 201 to 203 as shown in FIG. Reflected in the same direction as the direction. When the reflection of such light is viewed from the side, as shown in FIG. 5B, for example, the reflected light from the reflective tape 202 provided on the lower side of the screen 101 touches the input surface of the screen 101. Without being input to the image sensor 103 and detected. As a result, the image of the reflective tape taken by the image sensor 103 is as shown in FIG. This is the same as the received light image described with reference to FIG.

  On the other hand, if there is distortion or inclination in the reflective tape mounting part due to distortion or the like of the entire coordinate input device, the reflected light from the reflective tape 202 provided on the lower side of the screen 101 is incident on the input surface of the screen 101 and reflected. Then, it is input to the image sensor 103. The state of the reflected light in such a case is shown in FIG. As a result, the image of the reflective tape taken by the image sensor 103 is different from the case shown in FIG. 5C, as shown by hatching in FIG. A virtual image is generated. The direction of deviation in this case is the width direction of the reflective tape.

  When the input means 105 that is the pointing object is placed in the region where the light deviation occurs as described above, a shadow is generated in one or both of the real image and the virtual image. Usually, the detection of the shadow of the input means 105, which is the pointing object in the photographed image, is performed by checking whether there is a shadow at a predetermined position in the width direction of the photographed reflective tape, and if there is a shadow, the reflection tape Therefore, if there is a light shift, it is difficult to capture the position and size of the input means 105 that is the original pointing object. It may cause misalignment or malfunction.

  Moreover, although the LED etc. which radiate | emit directional light are used for the light source, since the emitted light has a breadth of several to several dozen degrees normally, incident light and reflected light are strict. The light which does not correspond to this is generated, and this becomes one of the causes of the optical axis deviation, which causes the detected coordinate deviation and malfunction as described above. Furthermore, retroreflected light may deviate from the input light due to distortion and tilt of the reflective tape mounting part due to distortion of the entire coordinate input device, foreign matter and dirt on the reflective tape, and deviation of the optical axis of the light source installation part. This is one of the causes of malfunctions.

  FIG. 6 is a diagram for explaining generation of a virtual image when the light reflected by the reflective tape is detected by the image sensor after being reflected by the input surface and the back surface of the cover in the vicinity of the cover position. Here, description will be made assuming that imaging is performed by the image sensor 103 installed in the upper right corner of the screen 101.

  As already described, the cover 401 is attached to the upper part of the screen 101 so as to cover the image sensors 102 and 103 and the control board 104 constituting the position detection apparatus 100, so that the cover 401 is installed in the vicinity of the image sensor 103. The light passing through the vicinity of the cover position from the light source is reflected by the reflective tape 201 provided on the left side of the screen 101 as shown in FIG. When such reflection of light is viewed from above, as shown in FIG. 6B, for example, the reflected light from the reflective tape 202 provided on the lower side of the screen 101 touches the input surface of the screen 101. Without being input to the image sensor 103 and detected. As a result, the image of the reflective tape taken by the image sensor 103 is as shown in FIG.

  On the other hand, if the reflection tape mounting portion due to distortion or the like of the entire coordinate input device is distorted or tilted, the reflected light from the reflection tape 202 provided on the lower side of the screen 101 is reflected on the input surface of the screen 101 or the back surface of the cover 401. Is input to the image sensor 103 after being reflected.

  FIG. 6D shows the state of the reflected light reflected from the back surface of the cover. As a result, the image of the reflective tape photographed by the image sensor 103 is a portion where the cover 401 of the image of the reflective tape 201 on the left side of the screen exists, as shown by hatching in FIG. This is different from the case shown in (c), and a virtual image is generated on the image sensor 103. The direction of deviation in this case is the width direction of the reflective tape.

  Moreover, the state of the reflected light reflected by the input surface is shown in FIG. As a result, the image of the reflective tape taken by the image sensor 103 is different from the case shown in FIG. 6C, as shown by hatching in FIG. A virtual image is generated. The direction of deviation in this case is the width direction of the reflective tape.

  FIG. 7 is a diagram illustrating a method for preventing the occurrence of a virtual image as described above in the embodiment of the present invention.

  In the embodiment of the present invention, an antireflection material is used at a position where light such as the input surface or the back surface of the cover is reflected, or an antireflection process is performed to prevent generation of a virtual image captured by the image sensor, or Try to reduce.

  That is, in the embodiment of the present invention, as shown in FIG. 7A, a reflection film is applied to the input surface of the screen 101 or UV processing is performed to prevent light reflection. ing. In the embodiment of the present invention, fine irregularities may be processed on the input surface by a method such as roughening, and light reflected irregularly may be reduced by irregularly reflecting the light. .

  Also, the inner surface of the cover 401 is processed in the same manner as described above. The back surface of the cover protecting the image sensor, the control board, and the like is particularly at a position where the reflection of light reflected at the center of the back surface of the cover is taken into the image sensor as a virtual image. For this reason, as shown in FIG. 7 (b), the back surface of the cover only needs to be processed in the same manner as described above only at a specific position near the center. It is possible to perform the processing at a lower cost than the processing.

  In the embodiment of the present invention, it is also possible to use a light absorbing material according to the characteristics of the light source. For example, in general, infrared light having a long wavelength and strong directivity may be used as a light source. In this case, a widely known infrared absorbing material may be used.

  An appearance of the coordinate input device according to the embodiment of the present invention configured by attaching the cover 401 to the screen as described above is as shown in FIG.

It is a block diagram which shows the structure of the coordinate input device using the position detection apparatus by one Embodiment of this invention. It is a figure explaining the attachment state of an image sensor, a light source, and a reflective tape. It is a figure explaining the outline of a position detection method with the angle of view of an image sensor, and the example of a captured image. It is a figure which shows schematic structure of the cover of a position detection apparatus. It is a figure explaining the production | generation of a virtual image when the light reflected by the reflective tape is detected by the image sensor after being reflected by the input surface. It is a figure explaining the production | generation of the virtual image when the light reflected by the reflective tape is detected by the image sensor after being reflected by the input surface and the back of the cover near the cover position. It is a figure explaining the method of preventing generation | occurrence | production of the virtual image in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Position detection apparatus 101 Screen 102, 103 Image sensor 104 Control board 105 Pointing object 106 Display control apparatus 107 Arithmetic apparatus 201-203 Reflective tape 204 Light source 205 Image sensor light-receiving surface 401 Cover

Claims (3)

In the position detection device that detects the position of the input means that is the pointing object located on the input surface of the coordinate input device,
A plurality of image sensors provided at at least two positions on the side, upper or lower side of the input surface of the coordinate input device, and installed in the vicinity of the image sensor, and light is transmitted along the input surface of the coordinate input device. A light source that irradiates the input surface so as to cover the entire input surface, a retroreflective reflective tape that is installed at a right angle to the input surface so as to surround the input surface of the coordinate input device, and an image captured by the image sensor Control means for performing image processing using a signal as input and calculating the coordinates of the indicated position on the input surface indicated by the input means;
An anti-reflection process is performed on the input surface of the coordinate input device.   The position detection device according to claim 1, wherein a cover is provided so as to cover the image sensor, the light source, and the control unit, and an antireflection process is applied to a back surface of the cover.   The position detecting device according to claim 2, wherein the portion of the back surface of the cover that has been subjected to antireflection processing is a region that includes a center portion of the back surface of the cover.

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