JP2001290584A - Optical digitizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical digitizer in which the reflection efficiency of retroreflected light from a retroreflection member nearby diagonals of light sources is increased, a winder detection area for the size of the device is secured and the manufacture cost of which is suppressed. SOLUTION: The optical digitizer which detects the indication position coordinates of an indication body on a detection surface comprises the light source which emit light beams, the retroreflection member which recursively reflects the light beams emitted by the light source provided at the circumference of the detection surface, an imaging means which detects which detects the direction of a shadow formed by cutting off the retroreflected light from the retroreflection member by the indication body, an image forming lens which images the retroreflected light on the imaging means, and an incidence angle varying means which refracts the light made incident on the retroreflection member nearby the diagonals of the light sources from the light sources and varies the angle of incidence on the retroreflection member. As the incidence angle varying means, for example, a Fresnel beam splitter, etc., is usable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-blocking type optical digitizer for detecting a pointing position coordinate of a pointer on a detection surface, and more particularly to a retroreflecting light from a retroreflecting member near a diagonal of a light source. The present invention relates to an optical digitizer having improved reflection efficiency.

[0002]

2. Description of the Related Art In recent years, an optical digitizer having more accurate detection capability has attracted attention instead 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 partial cross-sectional side view thereof. As shown in the figure, when a finger 2 serving as a pointer is placed on the detection surface 1, two detection units 3 provided above the detection surface 1 detect the pointing position coordinates based on the principle of triangulation. is there. The detection unit 3 is as shown in FIG.
As shown in FIG. 1, a half mirror or a tunnel mirror 12 is added in front of the imaging lens 9 of the linear image sensor 13 so that the optical axis of the LED light source 11 becomes linear image sensor 13.
Are arranged so as to be coincident with the optical axis. When there is nothing blocking light on the detection surface 1, light from the detection unit 3 passing through the detection surface 1 and entering the retroreflective member 22 passes through the opposite optical path and enters the detection unit 3. Come back. When the finger 2 or the like is placed on the detection surface 1, a part of the light path of light is blocked, and the light does not return to the detection unit 3. Since the shadow portion can be imaged by the image sensor 13, the direction in which the light is blocked can be detected by detecting the direction of the shadow. 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 pointing 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 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 characteristics are not perfect, the retroreflection characteristics deteriorate for light incident at a shallow angle (large incident angle). Therefore, the incident angle of light to the retroreflective member at the diagonal point farthest from the detection unit becomes the largest, and the retroreflected light from that area becomes weaker. When trying to detect the body, the difference between the shadow portion and the retroreflected light portion is reduced, so that the detection sensitivity is reduced. Therefore, an LED or the like having 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 retroreflection characteristics are improved by curving the corner 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.

In another conventional example shown in FIG. 8, a retroreflective characteristic is improved by providing a sawtooth-shaped retroreflective portion 23 near a retroreflective member 22 at a 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, 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-shaped retroreflective portion 23 is provided in a portion where the incident angle becomes large in the conventional example.

[0005]

However, in the conventional example shown in FIG. 7, since the corners of the diagonal retroreflective member 22 of the detection unit 3 are curved, the size of the device is the same as that in the case where it is not curved. If so, the detection area was narrow. Conversely, in order to realize a detection surface of the same size, it is unavoidable that the apparatus becomes large. Further, since the corners of the retroreflective member must be curved, the degree of freedom in designing the device is impaired.

The conventional examples shown in FIGS. 8 and 9 are not suitable for miniaturization because a further saw-toothed retroreflector 23 is required, and the number of manufacturing steps is increased because a sawtooth retroreflector must be provided. The cost was undeniable.

In view of such circumstances, the present invention can maintain good detection sensitivity at any place on the detection surface without using expensive large-intensity LEDs and the like, and the size of the detection area with respect to the size of the apparatus can be maintained. It is an object of the present invention to provide an optical digitizer that can reduce the size of the device itself because it can secure a wider range, and can also reduce the manufacturing cost.

[0008]

In order to achieve the above-mentioned object of the present invention, an optical digitizer according to the present invention for detecting the coordinates of a designated position of a pointer on a detection surface includes a light source for emitting a light beam. A retroreflecting member for retroreflecting a light beam emitted from the light source provided around the detection surface, and detecting a direction of a shadow generated by the pointer blocking the retroreflected light from the retroreflecting member. Imaging means for imaging an imaging lens for imaging the retroreflected light on the imaging means, and refracting light incident on the retroreflective member near the diagonal of the light source from the light source; Incident angle changing means for changing the incident angle to the retroreflective member.

The incident angle changing means is composed of a Fresnel beam splitter, a lenticular lens, or a prism sheet provided on a part or the whole of the front surface of the retroreflective member, and further, a transmission scattering film.

According to the above means, good detection sensitivity can be maintained at any place in the detection plane, and the size of the detection area can be made wider than the size of the apparatus. The effect that can be obtained.

[0011]

Embodiments of the present invention will be described below 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, portions denoted by the same reference numerals as those used in the conventional example represent the same components. The detection unit 3 may have a configuration as shown in FIG. 7B of the conventional example, but it is needless to say that the detection unit 3 is configured to emit light and receive retroreflection light from the retroreflection member. For example, various applications are possible, for example, a configuration in which a light source and an imaging lens are arranged close to each other, and a configuration in which a plurality of LEDs are arranged. The step of detecting the coordinates of the indicated position when the pointer is placed on the detection surface is the same as in the related art. That is, when there is nothing blocking light on the detection surface 1, the detection unit 3 passes through the detection surface 1 through the retroreflective member 2.
The light incident on 2 returns to the detection unit 3 through the opposite optical path. When the finger 2 or the like is placed on the detection surface 1, a part of the light path of light is blocked, and the light does not return to the detection unit 3. 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. This detection is performed by the detection units 3 and 3 at two different known positions, thereby calculating the coordinates of the pointing position of the finger 2 based on the principle of triangulation.

The feature of this embodiment is that a Fresnel beam splitter 30 is provided on the front surface of a retroreflective member 22, as shown in FIG. The Fresnel beam splitter 30 is an optical lens having the characteristics shown in FIG. 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 is formed by engraving a large number of parallel opposing small surfaces having the same angle, and has a characteristic of refracting incident light as shown. Due to this characteristic,
When light is incident on the retroreflective member 22 near the diagonal of the detection unit 3, incident light incident at a shallow angle is refracted by the Fresnel beam splitter 30 and is deeply incident on the retroreflective member 22 as shown in FIG. It is incident at an angle. Therefore, excellent retroreflection light can be obtained even at a corner where the amount of retroreflection light has been reduced due to incidence at a shallow angle. Therefore, there is no need to curve the retroreflective member or provide a sawtooth-shaped retroreflective member, so that the retroreflective member can be provided adjacent to the detection area, and the size of the detection surface relative to the size of the device itself is increased. It is possible to take. Therefore, even when the apparatus is downsized, it is possible to secure a sufficient detection area. Further, since sufficient retroreflection light can be obtained without using an expensive LED having a large amount of light, it can be manufactured at low cost.

The Fresnel beam splitter 30
Light incident at a deep angle has the characteristic of being refracted and emitted at a slightly larger angle. Therefore, 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 at a position far away from the diagonal of the detection unit 3 becomes stronger to some extent, and the reflected light from the retroreflective member 22 at a position directly below the detector unit 3 becomes somewhat weaker. 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 detection of the shadow portion and the reflected light portion by the finger 2 becomes easy. In addition, by arranging the flat portion of the Fresnel beam splitter on the detection surface side and the surface on which the small surface is cut toward the retroreflection member side, the frame around the detection surface becomes flat, so the retroreflection member There is no clogging of dust on the front. In addition, since the Fresnel beam splitter is formed in a sheet shape, it is only necessary to stick the Fresnel beam splitter on the front surface of the retroreflective member.

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.
That is, it may be provided only on the front surface of a part of the retroreflective member at the diagonal position of the detection unit.

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 an extremely thin and fine semi-cylindrical shape or a lens array optically equivalent thereto. Thereby, the same operation and effect as in the above-described example can be obtained.

Further, a prism sheet can be used other than the Fresnel beam splitter and the lenticular lens. FIG. 4 shows an optical digitizer of the present invention using a prism sheet. 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 is formed by forming a number of parallel grooves having a constant prism angle, and the incident light is refracted at a constant angle. FIG. 4 shows a prism sheet having such characteristics.
As shown in the figure, it is provided on the front surface of the retroreflective member 22. Here, since the prism sheet is refracted at a fixed angle, as shown in the figure, on the front surface of the retroreflective member 22 at the bottom of the detection surface 1, the prism sheets 31a, 31a, A prism sheet 31c, 3 is provided on the front surface of the retroreflective member 22 on both sides of the detection surface 1.
It is desirable to arrange 1d as shown.
With this configuration, the retroreflection 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. Detection becomes easier. 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. The process of detecting the coordinates of the designated position when the finger 2 is placed on the detection surface 1 is the same as that in the above-described example, and thus the description is omitted. As described above, even if a prism sheet is used, there is no need to curve the retroreflective member or to provide a sawtooth retroreflective member. Can be increased in size of the detection surface. In other words, it is possible to secure a sufficient detection area even when the device is downsized.

FIG. 6 shows another embodiment of the optical digitizer of the present invention. The illustrated example is obtained by applying the present invention to the conventional example shown in FIG. That is, an optical digitizer in which a mirror 24 is provided below the detection surface 1 using a laser as a light source of the detection unit 3 and a retroreflection member 22 is provided on the other two sides. A prism sheet 31 is disposed on the front surface as an incident angle changing means. The operation and effect when the prism sheet 31 is provided are as described above, and the description is omitted. In addition, other incident angle changing means, such as a Fresnel beam splitter or a lenticular lens, may be used instead of the prism sheet 31.

Further, 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 becomes possible to make the shallow incident light from the light source deep and make it incident on the retroreflective member, similarly to the incident angle changing means described so far.

The optical digitizer according to the present invention is not limited to the above-described example, but may be variously modified without departing from the gist of the present invention. For example, as the optical means for improving the angle of incidence on the retroreflective member, a Fresnel beam splitter, a lenticular lens, a prism sheet, a transmission scattering film, and the like have been exemplified, but the present invention is not limited to this, and shallow light incidence is possible. Various applications are possible 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]

As described above, according to the optical digitizer of the present invention, good detection sensitivity can be maintained at any place on the detection surface without using expensive large-amount LEDs or the like. Since the size of the detection area with respect to the size can be secured more widely, an excellent effect of providing an optical digitizer that can reduce the size of the device itself and reduce the manufacturing cost can be obtained.

[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 characteristics of a Fresnel beam splitter.

FIG. 3 is a diagram for explaining that light incident 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 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;
It is a figure which shows the thing where the corner part of a retroreflective member is curved.

FIG. 8 is a diagram illustrating another conventional optical digitizer, in which a sawtooth-shaped retroreflective portion is provided at a corner of a retroreflective member.

FIG. 9 is a diagram showing still another conventional optical digitizer, in which a sawtooth-shaped retroreflective portion is provided at a corner of a 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 Sawtooth retroreflector 24 Mirror 30 Fresnel beam splitter 31 Prism sheet

Claims (5)

[Claims] 1. An optical digitizer for detecting a pointing position coordinate of a pointer on a detection surface, wherein the optical digitizer is emitted from a light source for emitting a light beam and the light source provided around the detection surface. A retroreflecting member that retroreflects the reflected light beam; an imaging unit for detecting a direction of a shadow generated when the pointer blocks the retroreflecting light from the retroreflecting member; and the retroreflecting light to the imaging unit. An imaging lens for forming an image, and an incident angle changing unit that refracts light incident on the retroreflective member near the diagonal of the light source from the light source and changes the incident angle on the retroreflective member. An optical digitizer comprising: 2. The optical digitizer according to claim 1, wherein said incident angle changing means comprises a Fresnel beam splitter provided on a part or the whole of the front surface of said retroreflective member. . 3. An optical digitizer according to claim 1, wherein said incident angle changing means comprises a lenticular lens provided on a part or the whole of the front surface of said retroreflecting means. . 4. The optical digitizer according to claim 1, wherein said incident angle changing means comprises a prism sheet provided on a part or the whole of a front surface of said retroreflecting means. 5. An optical digitizer according to claim 1, wherein said incident angle changing means is formed of a transmission / scattering film provided on a part or the whole of a front surface of said retroreflection means. Digitizer.