News Column

Patent Issued for Position Detecting Device and Electro-Optical Device

March 5, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- A patent by the inventor Onishi, Yasunori (Shiojiri, JP), filed on March 26, 2010, was published online on February 18, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8654101 is assigned to Epson Imaging Devices Corporation (JP).

The following quote was obtained by the news editors from the background information supplied by the inventors: "The present invention relates to position detecting devices and electro-optical devices, and more particularly, to configurations of devices that obtain position information regarding an object to be detected on the basis of values which have been optically detected.

"In typical display devices equipped with an electro-optical device such as a liquid crystal display body, a lighting device such as a backlight may be incorporated in order to make the display screen visible or enhance the visibility. In addition, in the display devices, the display screen may be provided with a pointed position detecting unit such as a touch panel. In this case, when a given position on the display screen is pointed by a pen, a finger or the like, the pointed position is detected and input into an information processing device or the like.

"As the pointed position detecting unit (positional coordinate inputting unit) such as a touch panel, electrostatic capacitive type touch panels, resistive film type touch panels or the like that mechanically or electrically detect the state of a contact on the display screen are known. In addition, optical touch panels are known in which a grid of infrared light beams is formed across the display screen and photosensors are correspondingly provided so as to detect the infrared light beams, so that, when a finger or the like interrupts infrared light beams, the positional coordinates of the finger or the like can be detected. In general, various types of optical touch panels are known, and examples of the optical touch panels include the ones disclosed in JP-A-2004-295644 and JP-A-2004-303172.

"However, in the optical touch panels described above, it is necessary to arrange, adjacent to the display screen, multiple light sources and photosensors, optical switches, or light guide structures or the like in order to support the resolution of positional coordinates to be detected. This increases the number of optical elements, whereby there is a problem in that the manufacturing cost is increased and more power is consumed."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventor's summary information for this patent: "An advantage of some aspects of the invention is that a position detecting device and an electro-optical device (display device) are realized, in which an optical position detecting unit can be configured at low cost and so as to have lower power consumption.

"A position detecting device according to a first aspect of the invention includes a light guide plate that is configured to transmit therethrough light beams entering from a light incident face thereof and to emit the light beams from a light emitting face intersecting the light incident face, multiple light sources for position detection that are arranged along the light incident face and that discharge position detection light beams toward the light incident face, a photosensor that detects position detection light beams reflected by an object to be detected among the position detection light beams emitted from the light emitting face, a light source control unit that switches between a first driving mode and a second driving mode, the first driving mode being a mode in which discharged light intensities of the multiple light sources for position detection are gradually decreased toward one side of an arrangement direction of the multiple light sources for position detection and in which emitted light intensities of the position detection light beams emitted from the light emitting face exhibit a first light emission distribution tilted toward the one side of the arrangement direction, the second driving mode being a mode in which discharged light intensities of the multiple light sources for position detection are gradually decreased toward another side opposite the one side of the arrangement direction and in which emitted light intensities of the position detection light beams emitted from the light emitting face exhibit a second light emission distribution tilted toward the other side of the arrangement direction, and a position information derivation unit that derives position information regarding the object to be detected along the arrangement direction on the basis of output components of the photosensor respectively attributable to the first light emission distribution and the second light emission distribution.

"According to the first aspect of the invention, the light source control unit controls the multiple light sources for position detection so as to form, as light intensity distributions of the position detection light beams emitted from the light emitting face of the light guide plate, a first light emission distribution and a second light emission distribution respectively tilted toward the one side and the other side of the arrangement direction of the multiple light sources for position detection along the light incident face of the light guide plate. When both light emission distributions are formed, at least some of the light beams reflected by the object to be detected are detected for both light emission distributions by the photosensor, and values corresponding to the respective light intensities detected are output. The outputs of the photosensor vary depending on the position of the object to be detected in the arrangement direction in accordance with the tilts of both light emission distributions that the emitted light intensities exhibit along the arrangement direction. Thus, position information regarding the object to be detected in the arrangement direction can be determined on the basis of the output components of the photosensor attributable to the respective light emission distributions. In particular, when the light beams that are based on the first light emission distribution and the second light emission distribution and that are reflected by the object to be detected are detected by the photosensor and position information regarding the object to be detected in the arrangement direction is determined on the basis of the output components attributable to the respective distributions, the position information is less influenced by the outside light beams and level fluctuations in emitted light intensities or reflected light intensities, whereby the accuracy and the reproducibility of the position information can be enhanced.

"According to the first aspect of the invention, as described above, the multiple light sources for position detection that discharge position detection light beams are arranged on the light incident face of the light guide plate, and are driven by the light source control unit to form the first light emission distribution and the second light emission distribution respectively tilted toward the opposite sides from each other, and the light beams reflected by the object to be detected of both light emission distributions are detected by the photosensor. Therefore, there is no need to prepare the light sources for position detection and photosensors in a number corresponding to the resolution, whereby the number of elements needed can be reduced and also the power consumption can be reduced. Consequently, the optical position detecting unit can be configured at low cost and so as to have low power consumption.

"In this case, the method of deriving position information regarding the object to be detected on the basis of the output components of the photosensor attributable to the respective light emission distributions may be any method. Examples of such a method may include not only a method in which the position information is obtained directly by using the ratio or difference of the output components of the photosensor attributable to the respective light emission distributions, but also a method in which, when the level of one of the light emission distributions is changed so that the output components match each other of the photosensor attributable to the respective light emission distributions, the position information regarding the object to be detected is derived on the basis of the amount of change in the level.

"It is preferable that the light source control unit alternately forms the first light emission distribution and the second light emission distribution. Therefore, detection of the reflected light beams by the photosensor on the basis of the first light emission distribution and detection of the reflected light beams by the photosensor on the basis of the second light emission distribution can be performed successively, whereby both detections can be performed in a close time period. Especially in the case where the driving of the light sources for position detection for forming the first light emission distribution and the driving of the light sources for position detection for forming the second light emission distribution are performed in reverse phase on the basis of a predetermined drive period, the output components attributable to the respective light emission distributions can be easily distinguished from each other by phase analysis of detection signals of the photosensor.

"It is also preferable that the light guide plate includes two light incident faces facing each other with the light emitting face therebetween, that the multiple light sources for position detection are arranged along the two light incident faces, and that the light source control unit forms the first light emission distribution and the second light emission distribution by gradually decreasing the discharged light intensities of the light sources for position detection arranged along the two light incident faces simultaneously toward the same side of the arrangement direction. In this case, uniformity in the light emission distribution of the position detection light beams in a direction intersecting the arrangement direction can be increased, whereby the position information regarding the object to be detected in the arrangement direction can be obtained more accurately.

"In this case, it is preferable that, by alternately driving two groups of light sources for position detection arranged along the two light incident faces, the light source control unit alternately forms a third light emission distribution tilted toward one side of a direction intersecting the arrangement direction and a fourth light emission distribution tilted toward the other side opposite the one side of the direction intersecting the arrangement direction, and that the position information derivation unit derives position information regarding the object to be detected along the direction intersecting the arrangement direction on the basis of output components of the photosensor respectively attributable to the third light emission distribution and the fourth light emission distribution. With this configuration, by using the same light sources for position detection, both position information regarding the object to be detected along the arrangement direction of the light sources for position detection and position information regarding the object to be detected along the direction intersecting this arrangement direction can be obtained. That is, the obtaining of plan position information regarding the object to be detected can be realized.

"Note that, there is a case where the light source control unit forms the first light emission distribution by using a first group of multiple light sources for position detection, among the above-described multiple light sources for position detection, arranged so as to be spaced apart from one another in the arrangement direction and forms the second light emission distribution by using a second group of multiple light sources for position detection different from the first group of light sources for position detection, arranged so as to be spaced apart from one another in the arrangement direction. In addition, there is a case where the light source control unit forms both the first and second light emission distributions by using all of the multiple light sources for position detection. In the former case, the light sources can be controlled easily since the first light emission distribution and the second light emission distribution are formed by different light sources for position detection. In the latter case, the tilts of both light emission distributions can be realized more accurately since the light emission distributions are formed by using all of the light sources for position detection.

"An electro-optical device according to a second aspect of the invention includes a light guide plate that is configured to transmit therethrough light beams entering from a light incident face thereof and to emit the light beams from a light emitting face intersecting the light incident face, multiple light sources for position detection that are arranged along the light incident face and that discharge position detection light beams toward the light incident face, a photosensor that detects at least some of position detection light beams reflected by an object to be detected among the position detection light beams emitted from the light emitting face, a light source control unit that switches between a first driving mode and a second driving mode, the first driving mode being a mode in which discharged light intensities of the multiple light sources for position detection are gradually decreased toward one side of an arrangement direction of the multiple light sources for position detection and in which emitted light intensities of the position detection light beams emitted from the light emitting face exhibit a first light emission distribution tilted toward the one side of the arrangement direction, the second driving mode being a mode in which discharged light intensities of the multiple light sources for position detection are gradually decreased toward another side opposite the one side of the arrangement direction and in which emitted light intensities of the position detection light beams emitted from the light emitting face exhibit a second light emission distribution tilted toward the other side of the arrangement direction, a position information derivation unit that derives position information regarding the object to be detected along the arrangement direction on the basis of output components of the photosensor respectively attributable to the first light emission distribution and the second light emission distribution, and an electro-optical panel that has a display area arranged so as to overlap in plan view the light emitting face of the light guide plate.

"It is preferable that the display area is arranged at the light emitting side of the light emitting face with respect to the light guide plate, that the electro-optical device further includes multiple light sources for lighting that discharge illumination light beams toward the light incident face of the light guide plate, and that the multiple light sources for lighting are arranged, together with the multiple light sources for position detection, so as to be spaced apart from one another along the light incident face. With this configuration, the display area of the electro-optical device arranged at the light emitting side of the light guide plate can be illuminated since the multiple light sources for lighting are arranged so as to be spaced apart from one another along the light incident face and thus the light emitting face also emits the illumination light beams concurrently. Therefore, both the position detection function and the illumination function can be realized by using a common light guide plate, whereby the number of parts can be reduced and a compact electro-optical device can be realized.

"In this case, the light guide plate has a planar shape having multiple sides on which the light incident face is located, and the light incident face that the position detection light beams enter and the light incident face that the illumination light beams enter are located on different sides. In this case, as with the above-described embodiment, both the position detection function and the illumination function can be realized by using a common light guide plate, whereby the number of parts can be reduced and a compact electro-optical device can be realized. Additionally, in this case, since the light incident face that the position detection light beams enter and the light incident face that the illumination light beams enter are located at the different sides of the light guide plate, the light sources for position detection and the light sources for lighting can be arranged freely in accordance with light distribution properties required thereby. Especially in the case where the shape of the light guide plate in plan view is rectangular, it is preferable that the light incident face on which the multiple light sources for position detection are arranged and the light incident face on which the multiple light sources for lighting are arranged are located on sides adjacent to each other. In this case, since the illumination light beams and the position detection light beams are transmitted in different directions through the inside of the light guide plate, light guiding properties of the light guide plate for the illumination light beams and for the position detection light beams can be designed separately. In particular, as described later, it is preferable that the multiple light sources for position detection are arranged along shorter sides and the multiple light sources for lighting are arranged along longer sides.

"It is also preferable that the display area is arranged at the light emitting side of the light emitting face with respect to the light guide plate, that the electro-optical device further includes multiple light sources for lighting that discharge illumination light beams toward a face of the light guide plate at the opposite side from the light emitting face, and that the multiple light sources for lighting are arranged so as to be spaced apart from one another in an area overlapped in plan view with the light emitting face. In this case, so-called a direct-lighting illumination structure is provided, and the illumination light beams discharged from the light sources for lighting arranged so as to be spaced apart from one another in the area overlapped in plan view with the light emitting face pass through the light guide plate and illuminate the display area of the electro-optical panel."

URL and more information on this patent, see: Onishi, Yasunori. Position Detecting Device and Electro-Optical Device. U.S. Patent Number 8654101, filed March 26, 2010, and published online on February 18, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=59&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=2912&f=G&l=50&co1=AND&d=PTXT&s1=20140218.PD.&OS=ISD/20140218&RS=ISD/20140218

Keywords for this news article include: Electronics, Electro-optics, Epson Imaging Devices Corporation.

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Source: Electronics Newsweekly


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