JP3846544B2 - Optical digitizer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light-blocking type optical digitizer that detects the pointing position coordinates of a pointer on a detection surface, and in particular, light with improved reflection efficiency of retroreflected light from a retroreflective member near the diagonal of a light source. Regarding digitizers.
[0002]
[Prior art]
Recently, an optical digitizer having a more accurate detection capability has attracted attention in place of a resistive film type or electromagnetic induction type digitizer. FIG. 7 shows an example of a conventional optical digitizer. FIG. 7A is a schematic plan view of the optical digitizer, and FIG. 7B is a side view of a partial cross section thereof. As shown in the figure, when a finger 2 as an indicator is placed on the detection surface 1, the indicated position coordinates are detected by the principle of triangulation by two detection units 3 provided above the detection surface 1. is there. As shown in FIG. 7B, the detection unit 3 includes a half mirror or tunnel mirror 12 in front of the imaging lens 9 of the linear image sensor 13 so that the optical axis of the LED light source 11 is the same as that of the linear image sensor 13. Each is arranged so as to coincide with the optical axis. When nothing is blocking the light on the detection surface 1, the light that has passed through the detection surface 1 and entered the retroreflective member 22 from the detection unit 3 passes through the reverse optical path to the detection unit 3. Come back. When the finger 2 or the like is placed on the detection surface 1, a part of the optical path of the light is blocked and the detection unit 3 cannot be returned. Since this shadow part can be imaged by the image sensor 13, by detecting the direction of the shadow, it is possible to detect the direction in which the light is blocked. That is, if the direction in which the finger 2 exists can be detected by the detection units 3 and 3 at two different known positions, the indicated position coordinates of the finger 2 can be calculated based on the principle of triangulation.
[0003]
Here, the retroreflective member refers to a member having a reflection characteristic such that light incident thereon returns straight in the incident direction. As a typical retroreflective member, a retroreflective sheet in which a large number of small transparent glass beads are embedded, a small corner cube prism, or a white member having a high reflectance can be used. However, since the retroreflection characteristic is not perfect, the retroreflection characteristic is deteriorated for light incident at a shallow angle (large incident angle). Therefore, the incident angle of light to the retroreflective member located at the farthest diagonal from the detection unit is the largest, and the retroreflected light from that area becomes weak. If an attempt is made to detect the body, the difference between the shadow portion and the retroreflected light portion is reduced, so that the detection sensitivity is lowered. Therefore, an LED with a large amount of light may be used so that the shadow portion can be clearly seen. In the conventional example shown in FIG. 7, the retroreflective characteristic is improved by curving the corner portion of the retroreflective member 22 at the diagonal of the detection unit 3 so as to be incident at a deep angle (small incident angle). ing.
[0004]
In another conventional example shown in FIG. 8, the retroreflective characteristics are improved by providing a sawtooth retroreflective portion 23 in the vicinity of the retroreflective member 22 at the diagonal of the detection unit 3. Further, in another conventional example shown in FIG. 9, a laser is used as a light source of the detection unit 3 and a mirror 24 is provided below the detection surface 1 and a retroreflective member 22 is provided on the other two sides. Although this is an example of a digitizer, a sawtooth retroreflective portion 23 is also provided in a portion where the incident angle is increased in this conventional example as well.
[0005]
[Problems to be solved by the invention]
However, in the conventional example shown in FIG. 7, the corners of the diagonal retroreflective member 22 of the detection unit 3 are curved, so that the detection area is narrower if the size of the apparatus is the same as compared with the case where the diagonal unit is not curved. It was. In other words, if the detection surface having the same size is to be realized, it is inevitable that the apparatus becomes large. Moreover, since the corner | angular part of a retroreflection member must be curved, the freedom degree of the design of an apparatus was also impaired.
[0006]
The conventional examples shown in FIGS. 8 and 9 are not suitable for miniaturization because the sawtooth retroreflective portion 23 is further required, and the manufacturing process is increased because the sawtooth retroreflective portion has to be provided. I could not deny it.
[0007]
In view of such circumstances, the present invention can maintain good detection sensitivity at any location within the detection surface without using an expensive high-intensity LED or the like, and can further increase the size of the detection region relative to the size of the device. It is an object of the present invention to provide an optical digitizer that can be widely secured and can be downsized, and that can also reduce the manufacturing cost.
[0008]
[Means for Solving the Problems]
In order to achieve the above-described object of the present invention, an optical digitizer according to the present invention for detecting a pointing position coordinate of a pointer on a detection surface is provided around a light source for emitting a light beam and the detection surface. A retroreflective member that retroreflects the light emitted from the light source, an imaging unit for detecting a direction of a shadow caused by the indicator blocking the retroreflected light from the retroreflective member, and the imaging unit An imaging lens for imaging the retroreflective light, and refracting light incident on the retroreflective member near the diagonal of the light source from the light source to change the incident angle on the retroreflective member Incident angle changing means.
[0009]
The incident angle changing means includes any of a Fresnel beam splitter, a lenticular lens, a prism sheet, and a transmission scattering film provided on a part or the whole of the front surface of the retroreflective member.
[0010]
According to the above means, good detection sensitivity can be maintained at any location within the detection surface, and the size of the device itself can be reduced because the size of the detection area relative to the size of the device can be secured more widely. The effect is obtained.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a preferred embodiment of the optical digitizer of the present invention. In the figure, the same reference numerals as those used in the prior art denote the same parts. The detection unit 3 can be configured as shown in FIG. 7B of the conventional example. Of course, the detection unit 3 is configured to emit light and receive retroreflected light from the retroreflective member. For example, it is possible to adapt variously, for example, a device in which the light source and the imaging lens are arranged close to each other, a device in which a plurality of LEDs are arranged, and the like. The process of detecting the indicated position coordinates when the indicator is placed on the detection surface is the same as in the prior art. That is, when nothing is placed on the detection surface 1 to block the light, the light that has passed through the detection surface 1 and has entered the retroreflective member 22 from the detection unit 3 passes through the reverse optical path and passes through the detection unit 1. Come back to 3. When the finger 2 or the like is placed on the detection surface 1, a part of the optical path of the light is blocked and the detection unit 3 cannot be returned. The shadow portion is imaged by a light receiving element such as an image sensor of the detection unit, and the direction of the shadow is detected. By performing this detection with the detection units 3 and 3 at two different known positions, the designated position coordinates of the finger 2 are calculated based on the principle of triangulation.
[0012]
The feature of this embodiment is that a Fresnel beam splitter 30 is provided in front of the retroreflective member 22 as shown in FIG. The Fresnel beam splitter 30 is an optical lens having the characteristics shown in FIG. 2A is a sectional view of the Fresnel beam splitter 30, and FIG. 2B is a perspective view thereof. As shown in the figure, the Fresnel beam splitter has a large number of parallel opposing facets of the same angle, and has the property of refracting incident light as shown. Due to this characteristic, when light is incident on the retroreflective member 22 in the vicinity of the diagonal of the detection unit 3, the incident light incident at a shallow angle is refracted by the Fresnel beam splitter 30 and retroreflected as shown in FIG. It enters the member 22 at a deep angle. Therefore, good retroreflected light can be obtained even at the corners where the amount of retroreflected light has been reduced due to incidence at a shallow angle. Therefore, it is not necessary to bend the retroreflective member or provide a sawtooth retroreflective member, so the retroreflective member can be provided adjacent to the detection region, and the size of the detection surface relative to the size of the device itself can be increased. It becomes possible to take. Therefore, even when the apparatus is downsized, it is possible to ensure a sufficient detection area. In addition, since sufficient retroreflected light can be obtained without using an expensive large-intensity LED, it can be manufactured at low cost.
[0013]
Further, the Fresnel beam splitter 30 has a characteristic that light incident at a deep angle is refracted and emitted at a slightly larger angle. Accordingly, the light emitted directly below the detection unit 3 enters the Fresnel beam splitter 30 almost vertically, and is refracted here and enters the retroreflective member 22 at a slightly shallow angle. From these characteristics, the reflected light from the retroreflective member 22 located far from the diagonal of the detection unit 3 becomes somewhat strong, and the reflected light from the retroreflective member 22 located near the position directly below the detection unit 3 becomes weak to some extent. Therefore, the intensity of the reflected light from the retroreflective member received by the detection unit can be made uniform to some extent, and the shadow portion and the reflected light portion can be easily detected by the finger 2. In addition, the frame around the detection surface becomes flat by arranging the flat part of the Fresnel beam splitter on the detection surface side and the surface with the small surface facing the retroreflection member side, so the retroreflection member There is no clogging of garbage at the front. Further, since the Fresnel beam splitter is in the form of a sheet, the manufacturing cost can be reduced because it is only necessary to attach the Fresnel beam splitter to the front surface of the retroreflective member.
[0014]
In the illustrated example, the Fresnel beam splitter is provided on the entire front surface of the retroreflective member. However, the present invention is not limited to this, and the recursion is located at the corner of the retroreflective member, that is, at the diagonal position of the detection unit. You may provide only in the one part front surface of a reflection member.
[0015]
In the above example, the Fresnel beam splitter is provided on the front surface of the retroreflective member. However, a lenticular lens having the same characteristics as the Fresnel beam splitter may be provided on the front surface of the retroreflective member. The lenticular lens refers to a very thin fine semi-cylindrical shape or a lens array optically equivalent to this. Thereby, the same effect as the above-mentioned example is obtained.
[0016]
In addition to the Fresnel beam splitter and the lenticular lens, a prism sheet can be used. FIG. 4 shows an optical digitizer of the present invention when a prism sheet is used. As illustrated, a prism sheet 31 is provided on the front surface of the retroreflective member 22. FIG. 5A is a cross-sectional view of the prism sheet, and FIG. 5B is a perspective view thereof. As shown in the figure, the prism sheet has a large number of parallel grooves with a constant prism angle, and incident light is refracted at a constant angle. A prism sheet having such characteristics is provided on the front surface of the retroreflective member 22 as shown in FIG. Here, since the prism sheet is refracted at a certain angle, the prism sheet 31a, which is located on the front surface of the retroreflective member 22 at the bottom of the detection surface 1 in the left and right directions around the center of the detection surface as shown in the drawing. It is desirable to arrange 31b and arrange prism sheets 31c and 31d on the front surface of the retroreflective member 22 on both sides of the detection surface 1 as shown in the figure. With such a configuration, the retroreflective characteristics at the corners are improved, and the intensity of the reflected light from the retroreflective member received by the detection unit 3 is made uniform to some extent. Is easy to detect. However, similarly to the above-described embodiment, in this embodiment, a prism sheet may be provided only on the front surface of a part of the retroreflective member at the diagonal of the detection unit. In addition, since the process of detecting the designated position coordinates when the finger 2 is placed on the detection surface 1 is the same as the above example, the description thereof is omitted. In this way, even if a prism sheet is used, there is no need to bend the retroreflective member or provide a saw-toothed retroreflective member. Therefore, the retroreflective member can be provided adjacent to the detection region, and the size of the device itself. It is possible to increase the size of the detection surface for. In other words, a sufficient detection area can be secured even when the apparatus is downsized.
[0017]
FIG. 6 shows another embodiment of the optical digitizer of the present invention. In the illustrated example, the present invention is applied to the conventional example shown in FIG. That is, an optical digitizer in which a laser is used as the light source of the detection unit 3 and a mirror 24 is provided below the detection surface 1 and a retroreflective member 22 is provided on the other two sides. A prism sheet 31 is arranged on the front surface as incident angle changing means. The operational effects when the prism sheet 31 is provided are as described above, and a description thereof will be omitted. Of course, other incident angle changing means such as a Fresnel beam splitter or a lenticular lens may be used instead of the prism sheet 31.
[0018]
Furthermore, as the incident angle changing means, for example, a viewing angle widening film used in a liquid crystal display device can be used. This is a film having a characteristic of transmitting and scattering incident light in a specific direction, and can spread the incident light by the diffraction effect of the surface. By utilizing this characteristic, it is possible to make shallow incident light from the light source deeper and enter the retroreflective member, similarly to the incident angle changing means described so far.
[0019]
Note that the optical digitizer of the present invention is not limited to the above-described illustrated examples, and various modifications can be made without departing from the scope of the present invention. For example, as an optical means for improving the incident angle to the retroreflective member, a Fresnel beam splitter, a lenticular lens, a prism sheet, a transmission scattering film, etc. are illustrated, but the present invention is not limited to this, and the incident light is shallow. Various modifications can be applied as long as the incident angle is changed so that the incident light is refracted and incident on the retroreflective member at a deep angle.
[0020]
【The invention's effect】
As described above, according to the optical digitizer of the present invention, it is possible to maintain a good detection sensitivity anywhere in the detection surface without using an expensive large light quantity LED or the like, and a detection area with respect to the size of the apparatus. Therefore, it is possible to provide an optical digitizer capable of reducing the size of the apparatus itself and reducing the manufacturing cost.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of an optical digitizer of the present invention, showing an embodiment in which a Fresnel beam splitter is provided on the front surface of a retroreflective member.
FIG. 2 is a diagram for explaining the characteristics of a Fresnel beam splitter;
FIG. 3 is a diagram for explaining that incident light on a retroreflective member is refracted by a Fresnel beam splitter.
FIG. 4 is a schematic plan view of another optical digitizer of the present invention, showing an embodiment in which a prism sheet is provided on the front surface of a retroreflective member.
FIG. 5 is a diagram for explaining the characteristics of a prism sheet;
FIG. 6 is a schematic plan view of still another optical digitizer of the present invention.
FIG. 7 is a diagram showing a conventional optical digitizer, in which the corners of the retroreflective member are curved.
FIG. 8 is a view showing another conventional optical digitizer, in which a sawtooth retroreflective portion is provided at a corner of the retroreflective member.
FIG. 9 is a view showing still another conventional optical digitizer, in which a sawtooth retroreflective portion is provided at a corner of the retroreflective member.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Detection surface 2 Finger 3 Detection unit 9 Imaging lens 11 Light source 12 Tunnel mirror 13 Linear image sensor 22 Retroreflective member 23 Serrated retroreflective part 24 Mirror 30 Fresnel beam splitter 31 Prism sheet

Claims (5)

An optical digitizer for detecting the pointing position coordinates of the pointer on the detection surface, the optical digitizer,
A light source for emitting light;
A retroreflective member that retroreflects light rays emitted from the light source provided around the detection surface;
Imaging means for detecting a direction of a shadow produced by the indicator blocking retroreflected light from the retroreflective member;
An imaging lens for imaging the retroreflected light on the imaging means;
Incident angle changing means for refracting light incident on the retroreflective member near the diagonal of the light source from the light source and changing the incident angle on the retroreflective member;
An optical digitizer characterized by comprising 2. The optical digitizer according to claim 1, wherein the incident angle changing unit includes a Fresnel beam splitter provided on a part or the whole of the front surface of the retroreflective member. 2. The optical digitizer according to claim 1, wherein the incident angle changing means is a lenticular lens provided on a part or the whole of the front surface of the retroreflective means. 2. The optical digitizer according to claim 1, wherein the incident angle changing unit includes a prism sheet provided on a part of or the entire front surface of the retroreflective unit. 2. The optical digitizer according to claim 1, wherein the incident angle changing means is made of a transmission / scattering film provided on a part or the whole of the front surface of the retroreflective means.

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