Optical position detecting device, robot hand, and robot arm

In an optical position detecting device, a position detecting section detects the position of a target object on the basis of a result obtained by receiving detection light, which is emitted from a light source section and reflected by the target object, using a light detection section. As seen from an emitting direction of the detection light, the light detection section is located inside a region surrounded by a closed circuit passing through a plurality of the light source sections or inside a region pinched by the plurality of light source sections. The plurality of light source sections has a first light-emitting element, and a second light-emitting element located closer to the light detection section side than the first light-emitting element. The light source driving section alternately turns on the first light-emitting element and the second light-emitting element.

This application claims priority to Japanese Patent Application No. 2010-085819 filed Apr. 2, 2010 which is hereby expressly incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to an optical position detecting device which optically detects a target object.

2. Related Art

As an optical position detecting device which optically detects a target object, for example, as shown inFIG. 8, an optical position detecting device is suggested in which detection light L2is emitted toward the target object Ob via a translucent member40from two detection light source sections12, and detection light L3reflected by the target object Ob is transmitted through the translucent member40and is detected by a photodetector30. In this optical position detecting device, for example, if the two detection light source sections12are differentially moved on the basis of a detection result in the photodetector30, the ratio of the distance between one detection light source section12of the two detection light source sections12and the target object Ob and the distance between the other detection light source section12and the target object Ob is known. Accordingly, the position of the target object Ob can be detected (refer to JP-T-2003-534554 (FIG. 10)).

However, in the configuration shown inFIG. 8, in a case where the target object Ob is inside two detection light source sections12as shown as the target object Ob1and in a case where the target object Ob is outside the two detection light source sections12as shown as the target object Ob2, there is a problem in that the ratio of the distance between one detection light source section12of the two detection light source sections12and the target object Ob and the distance between the other detection light source section12and the target object Ob becomes equal. For this reason, when the ratio of the distance between one detection light source section12of the two detection light source sections12and the target object Ob and the distance between the other detection light source section12and the target object Ob is obtained, it cannot be determined whether the distance between the two detection light source sections12may be internally divided or externally divided.

SUMMARY

An advantage of some aspects of the invention is to provide an optical position detecting device which can detect whether a target object is outside or inside a region where a detection light source is arranged.

According to an aspect of the invention, there is provided an optical position detecting device which optically detects the position of a target object. The device includes a plurality of detection light source sections which emits detection light and is separated in a direction intersecting an emitting direction of the detection light; a photodetector which receives the detection light reflected by the target object located in an emitting-side space of the detection light; a light source driving section which sequentially turns on the plurality of detection light source sections; and a position detecting section which detects the position of the target object on the basis of a light-receiving result of the photodetector. As seen from the emitting-side space of the detection light, the photodetector is located inside the plurality of detection light source sections, and the plurality of detection light source sections includes an outer light-emitting element and an inner light-emitting element arranged inside where the photodetector is located to the outer light-emitting element, respectively. The position detecting section determines whether the target object is located either outside or inside the detection light source section on the basis of a comparison result between the light-receiving intensity in the photodetector when the outer light-emitting element is turned on and the light-receiving intensity in the photodetector when the inner light-emitting element is turned on.

In the aspect of the invention, the light source driving section sequentially turns on the plurality of detection light source sections, and the photodetector receives the detection light reflected by the target object during that time. Accordingly, if a detection result in the photodetector is directly used, or a driving current or the like when the two detection light source sections are differentially moved via the photodetector is used, the position detecting section can detect the position of the target object. Here, as seen from the emitting-side space, the photodetector is located inside the plurality of detection light source sections, and the plurality of detection light source sections includes an outer light-emitting element and an inner light-emitting element inside the outer light-emitting element, respectively. Accordingly, the position detecting section can determine whether the target object is located either outside or inside the detection light source section on the basis of a comparison result between the light-receiving intensity in the photodetector when the outer light-emitting element is turned on and the light-receiving intensity in the photodetector when the inner light-emitting element is turned on. For this reason, when the ratio of the distance between one detection light source section of the two detection light source sections and the target object and the distance between the other detection light source section and the target object is obtained, there is no doubt as to whether the distance between the two detection light source sections may be internally divided to specify the position of the target object or the distance between the two detection light source sections may be externally divided to specify the position of the target object. Therefore, the position of the target object can be accurately detected.

In the aspect of the invention, it is possible for the position detecting device to adopt a configuration in which, when the outer light-emitting element and the inner light-emitting element alternately emit light with the same intensity, the position detecting section determines that the target object is located outside the detection light source section if the light-receiving intensity in the photodetector when the outer light-emitting element emits light is larger than the light-receiving intensity in the photodetector when the inner light-emitting element emits light, and determines that the target object is located inside the detection light source section if the light-receiving intensity in the photodetector when the first light-emitting element emits light is smaller than the light-receiving intensity in the photodetector when the second light-emitting element emits light.

In the aspect of the invention, the position detecting device may adopt a configuration in which, when the outer light-emitting element and the inner light-emitting element alternately emit light with the same intensity, the position detecting section determines that the target object is located outside an intermediate position between the outer light-emitting element and the inner light-emitting element if the light-receiving intensity in the photodetector when the outer light-emitting element emits light is larger than the light-receiving intensity in the photodetector when the inner light-emitting element emits light, and determines that the target object is located inside the intermediate position between the outer light-emitting element and the inner light-emitting element if the light-receiving intensity in the photodetector when the first light-emitting element emits light is smaller than the light-receiving intensity in the photodetector when the second light-emitting element emits light.

In the aspect of the invention, it is preferable that, when the emitting direction of the detection light is defined as a Z-axis direction, and two directions intersecting the Z-axis direction are defined as an X-axis direction and a Y-axis direction, the plurality of detection light source sections includes a detection light source section separated in the X-axis direction, and a detection light source section separated in the Y-axis direction. According to this configuration, the X coordinate and Y coordinate of the target object can be detected.

In the aspect of the invention, it is preferable that the position detecting section detects the coordinate position of the target object on the basis of a result obtained by differentially moving some detection light source sections and other detection light source sections in the plurality of detection light source sections, on the basis of the light-receiving result of the photodetector. If such a differential movement is used, the influence of environmental light or the like can be automatically corrected.

In the aspect of the invention, it is preferable that the apparatus with a position detection function further includes a reference light source that emits reference light that enters the photodetector without travelling through the emitting-side space. The position detecting section detects the coordinate position of the target object on the basis of a result obtained by changing and differentially moving combinations of some detection light source sections of the plurality of detection light source sections and the light source for reference, on the basis of the light-receiving result of the photodetector. If such a differential movement is used, the influence of environmental light or the like can be automatically corrected.

In the aspect of the invention, it is preferable that the position detecting section detects the position of the target object in the emitting direction of the detection light on the basis of a light-receiving result in the photodetector when the plurality of detection light source sections is simultaneously or sequentially turned on.

In the aspect of the invention, it is preferable that the detection light is infrared light. According to this configuration, since the detection light is not viewed, the optical position detecting device can be used for various apparatuses, so as not to hinder the display even in a case where the optical position detecting device is applied to a display apparatus.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Next, embodiments of the invention will be described with reference to the accompanying drawings. In addition, in the following description, the axes which intersect each other will be described as the X-axis, the Y-axis, and the Z-axis, and the emitting direction of detection light will be described as the Z-axis direction. Additionally, in the drawings referred to below, one side of an X-axis direction is shown as X1side, the other side thereof is shown as X2side, one side of a Y-axis direction is shown as Y1side, and the other side thereof is shown as Y2side. Additionally, in the following description, corresponding constituent elements will be designated by the same reference numerals, and will be described so as to make correspondence to constituent elements shown inFIG. 8easily understood.

Overall Configuration

FIGS. 1A to 1Care explanatory views showing sections of an optical position detecting device to which the invention is applied, whereinFIGS. 1A,1B and1C are: an explanatory view showing a three-dimensional configuration of constituent elements of the optical position detecting device; an explanatory view showing a planar configuration of the constituent elements of the optical position detecting device; and an explanatory view when the constituent elements of the optical position detecting device are seen from the side.FIG. 2is an explanatory view showing the overall configuration of the optical position detecting device to which the invention is applied.

InFIGS. 1A to 1CandFIG. 2, the optical position detecting device10of the present embodiment is an optical device used as a tactile sensor in a robot hand unit or the like, and includes a light source unit11including a plurality of detection light source sections12which emit detection light L2toward the one side Z1in the Z-axis direction, and a photodetector30which detects detection light L3reflected by the target object Ob. Additionally, the optical position detecting device10may have a sheet-shaped or plate-shaped translucent member40. In this case, the detection light source sections12emit the detection light L2toward a first surface41from a second surface42side opposite to the first surface41side in the translucent member40, and the photodetector30detects the detection light L3which has been reflected by the target object Ob and has been transmitted through the second surface42side of the translucent member40. For this reason, a light-receiving portion31of the photodetector30faces the second surface42of the translucent member40.

In the present embodiment, the light source unit11includes a first detection light source section12A, a second detection light source section12B, a third detection light source section12C, and a fourth detection light source section12D as a plurality of detection light source sections12, and these detection light source sections12all have light-emitting portions which are directed toward the translucent member40. Accordingly, the detection light L2emitted from the detection light source sections12is transmitted through the translucent member40and is emitted to the first surface41side (the emitting-side space of the detection light L2from the light source unit11). In the present embodiment, a detection space10R where the position of the target object Ob is detected is constituted by this emitting-side space (the space on the side of the first surface41).

The first detection light source section12A, the second detection light source section12B, the third detection light source section12C, and the fourth detection light source section12D are arranged in this order around the central optical axis of the photodetector30as seen from the detection space10R (Z-axis direction), and the photodetector30is located inside the region surrounded by the plurality of detection light source sections12as seen from the detection space10R (Z-axis direction). In the plurality of detection light source sections12, the first detection light source section12A and the third detection light source section12C are separated from each other in the X-axis direction, and the second detection light source section12B and the fourth detection light source section12D are separated from each other in the Y-axis direction. In addition, the second detection light source section12B and the fourth detection light source section12D are also separated from each other in the X-axis direction with respect to the first detection light source section12A as seen from the first detection light source section12A, and the second detection light source section12B and the fourth detection light source section12D are also separated from each other in the X-axis direction with respect to the third detection light source section12C as seen from the third detection light source section12C. Similarly, the first detection light source section12A and the third detection light source section12C are also separated from each other in the Y-axis direction with respect to the second detection light source section12B as seen from the second detection light source section12B, and the first detection light source section12A and the third detection light source section12C are also separated from each other in the Y-axis direction with respect to the fourth detection light source section12D as seen from the fourth detection light source section12D.

Additionally, as seen from the detection space10R (Z-axis direction), the first detection light source section12A, the second detection light source section12B, the third detection light source section12C, and the fourth detection light source section12D are arranged at equal angular intervals about the photodetector30. Additionally, as seen from the detection space10R (Z-axis direction), the first detection light source section12A, the second detection light source section12B, the third detection light source section12C, and the fourth detection light source section12D have the same distance from the photodetector30.

Additionally, the light source unit11also includes a reference light source12R in which a light-emitting portion120ris directed to the photodetector30. The reference light source12R is constituted by an LED (light emission diode) or the like, and the reference light source12R emits reference light Lr of infrared light having a peak wavelength located within a range of 840 to 1000 nm as divergence light. Here, the reference light Lr emitted from the reference light source12R does not enter the first surface41side (detection space10R) of the translucent member40, but enters the photodetector30, without travelling through the detection space10R, by the orientation of the reference light source12R, a light-shielding cover (not shown) provided in the reference light source12R, or the like.

The photodetector30includes a photodiode, a photo transistor, or the like in which the light-receiving portion31is directed to the translucent member40. In the present embodiment, the photodetector30is a photodiode including a sensitivity peak of an infrared region.

Detailed Configuration of Detection Light Source Section12

In the optical position detecting device10of the present embodiment, each of a plurality of detection light source sections12includes two light-emitting elements lined up in the radial direction, as seen from the detection space10R (Z-axis direction). More specifically, first, the first detection light source section12A includes an outer light-emitting element12A1, and an inner light-emitting element12A2closer to the photodetector30side (inner side) than the outer light-emitting element12A1, and the outer light-emitting element12A1, the inner light-emitting element12A2, and the photodetector30are arranged on the same straight line. Additionally, the second detection light source section12B, similarly to the first detection light source section12A, also includes an outer light-emitting element12B1, and an inner light-emitting element12B2closer to the photodetector30side (inner side) than the outer light-emitting element12B1, and the outer light-emitting element12B1, inner light-emitting element12B2, and the photodetector30are arranged on the same straight line. Additionally, the third detection light source section12C, similarly to the first detection light source section12A, also includes an outer light-emitting element12C1, and an inner light-emitting element12C2closer to the photodetector30side (inner side) than the outer light-emitting element12C1, and the outer light-emitting element12C1, the inner light-emitting element12C2, and the photodetector30are arranged on the same straight line. Additionally, the fourth detection light source section12D, similarly to the first detection light source section12A also includes an outer light-emitting element12D1, and an inner light-emitting element12D2closer to the photodetector30side (inner side) than the outer light-emitting element12D1, and the outer light-emitting element12D1, the inner light-emitting element12D2, and the photodetector30are arranged on the same straight line.

Here, the outer light-emitting elements12A1to12D1are all located on the circumference of a radius r1with the photodetector30as a center, and the inner light-emitting elements12A2to12D2are all located on the circumference of a radius r2(here, r1>r2) with the photodetector30as a center. In addition, a circle with the radius r0(here, r0=(r1+r2)/2) located at the center between a circle with the radius r1and a circle with the radius r2is also expressed inFIG. 1B.

Here, the outer light-emitting elements12A1to12D1and the inner light-emitting elements12A2to12D2are respectively constituted by light-emitting elements, such as LEDs (light emission diodes), and emit the detection light L2(detection light L2ato L2d) of infrared light having a peak wavelength located within a range of 840 to 1000 nm as divergence light.

Configuration of Position Detecting Section or the Like

As shown inFIG. 2, the light source unit11includes a light source driving section14which drives the plurality of detection light source sections12. The light source driving section14includes alight source driving circuit140which drives the detection light source section12and the reference light source12R, and a light source controller145which controls on/off pattern of each of the reference light source12R and the detection light source section12via the light source driving circuit140. The light source driving circuit140includes light source driving circuits140ato140dwhich drive the first detection light source section12A to the fourth detection light source section12D, and a light source driving circuit140rwhich drives the reference light source12R. Additionally, the light source driving circuits140ato140dindividually drive the outer light-emitting elements12A1to12D1and the inner light-emitting elements12A2to12D2, respectively. The light source controller145controls all the light source driving circuits140ato140d, and140r. In addition, as for the light source driving circuits140ato140d, it is also possible to adopt a configuration in which the outer light-emitting elements12A1to12D1and the inner light-emitting elements12A2to12D2are individually driven by switching circuits. In this case, only one light source driving circuit140is required.

The position detecting section50is electrically connected to the photodetector30, and a detection result in the photodetector30is output to the position detecting section50. The position detecting section50includes a signal processor55for detecting the position of the target object Ob on the basis of the detection result in the photodetector30, and this signal processor55includes an amplifier, a comparator, or the like. Additionally, the position detecting section50includes XY coordinate detector52which detects the XY coordinates of the target object Ob, and the Z coordinate detector53which detects the Z coordinate of the target object Ob. Additionally, when the position detecting section50detects the X coordinate and Y coordinate of the target object Ob, the position detecting section also includes an inside/outside detector54which detects whether the target object Ob is located inside or located outside the detection light source section12. The position detecting section50and the light source driving section14which are configured in this way operate to interlock with each other, and perform the position detection which will be described below.

Principle of Inside/Outside Detection

FIGS. 3A to 3Eare explanatory views showing the principle of inside/outside determination of the target object Ob which is performed by the optical position detecting device10to which the invention is applied.

In the optical position detecting device10of the present embodiment, as will be described below with reference toFIGS. 4A to 5B, the ratio of the distance between one detection light source section12of the two detection light source sections12and the target object Ob and the distance between another detection light source section12and the target object Ob is obtained by the differential movement between the detection light source sections12or the differential movement between the detection light source section12and the reference light source12R, and the position of the target object Ob is detected on the basis of this ratio. Although any of the outer light-emitting elements12A1to12D1and the inner light-emitting elements12A2to12D2may be used during this differential movement, a case where the outer light-emitting elements12A1to12D1are used is illustrated in the following description.

Additionally, in the present embodiment, before and after the ratio of the distance between one detection light source section12of the two detection light source sections12and the target object Ob and the distance between the other detection light source section12, and the target object Ob is obtained by the differential movement, it is detected whether the target object Ob is located inside the two detection light source sections12as shown as a target object Ob1inFIG. 3Aor whether the target object Ob is located outside the two detection light source sections12as shown as a target object Ob2inFIG. 3A.

Hereinafter, an example of an inside/outside detection method will be described wherein the target object Ob is determined to be inside or outside the third detection light source section12C when the coordinates of the target object Ob are detected. In the present embodiment, first, the ratio of the distance between the outer light-emitting element12A1and the target object Ob and the distance between the outer light-emitting element12C1and the target object Ob is obtained by the differential movement between the outer light-emitting elements12A1and12C1or the differential movement between the outer light-emitting element12A1or12C1and the reference light source12R.

Additionally, before or after this ratio is obtained, the outer light-emitting element12C1and the inner light-emitting element12C2used for the third detection light source section12C are alternately turned on, and the detection light L2is made to emit with the same intensity. Then, in the inside/outside detector54, the light-receiving intensity in the photodetector30when the outer light-emitting element12C1is turned on and the light-receiving intensity in the photodetector30when the inner light-emitting element12C2is turned on is compared with each other. On the basis of this comparison result, it is detected whether the target object Ob is located either outside or inside the third light source section12C.

More specifically, as shown inFIG. 3B, in a case where the target object Ob is inside the third detection light source section12C, the distance between the target object Ob and the outer light-emitting element12C1is longer than the distance between the target object Ob and the inner light-emitting element12C2. Accordingly, the detection intensity in the photodetector30when the outer light-emitting element12C1is turned on is smaller than the light-receiving intensity in the photodetector30when the inner light-emitting element12C2is turned on. Accordingly, the inside/outside detector54can determine that the target object Ob is inside the third detection light source section12C. Therefore, when the XY coordinate detector52specifies the coordinates of the target object Ob on the basis of the ratio of the distance between the outer light-emitting element12A1and the target object Ob and the distance between the outer light-emitting element12C1and the target object Ob, the distance between the first detection light source section12A and the third detection light source section12C is internally divided.

On the other hand, as shown inFIG. 3E, in a case where the target object Ob is outside the third detection light source section12C, the distance between the target object Ob and the outer light-emitting element12C1is shorter than the distance between the target object Ob and the inner light-emitting element12C2. Accordingly, the detection intensity in the photodetector30when the outer light-emitting element12C1is turned on is larger than the light-receiving intensity in the photodetector30when the inner light-emitting element12C2is turned on. Accordingly, the inside/outside detector54can determine that the target object Ob is outside the third detection light source section12C. Therefore, when the XY coordinate detector52specifies the coordinates of the target object Ob on the basis of the ratio of the distance between the outer light-emitting element12A1and the target object Ob and the distance between the outer light-emitting element12C1and the target object Ob, the distance between the first detection light source section12A and the third detection light source section12C is externally divided.

In addition, in a case where the distance between the outer light-emitting element12C1and the inner light-emitting element12C2is narrow in the third detection light source section12C, as shown inFIGS. 3B and 3C, irrespective of whether the target object Ob is at any position near the outer light-emitting element12C1or the inner light-emitting element12C2, the detection error of the coordinates of the target object Ob is small even if the above method is adopted.

Here, in a case where the distance between the outer light-emitting element12C1and the inner light-emitting element12C2is large in the third detection light source section12C, the coordinates of the target object Ob may not be performed with a region surrounded by the circle with the radius r0(here, r0=(r1+r2)/2) located at the center between the circle with the radius r1and the circle with the radius r2as an effective region and with the outside of the region surrounded by the circle with the radius r0as an invalid region.

That is, as shown inFIG. 3C, in a case where the target object Ob is located in a region near the inner light-emitting element12C2between the outer light-emitting element12C1and the inner light-emitting element12C2, the distance between the target object Ob and the outer light-emitting element12C1is longer than the distance between the target object Ob and the inner light-emitting element12C2. Accordingly, when the outer light-emitting element12C1and the inner light-emitting element12C2used for the third detection light source section12C are alternately turned on and the detection light L2is made to emit with the same intensity, the detection intensity in the photodetector30when the outer light-emitting element12C1is turned on is smaller than the light-receiving intensity in the photodetector30when the inner light-emitting element12C2is turned on. Accordingly, the inside/outside detector54can determine that the target object Ob is inside a region surrounded by the circle with the radius r0, i.e., inside the outer light-emitting element12C1. Therefore, when the XY coordinate detector52specifies the coordinates of the target object Ob on the basis of the ratio of the distance between the outer light-emitting element12A1and the target object Ob and the distance between the outer light-emitting element12C1and the target object Ob, the distance between the first detection light source section12A and the third detection light source section12C is internally divided.

On the other hand, as shown inFIG. 3D, in a case where the target object Ob is located in a region near the outer light-emitting element12C1between the outer light-emitting element12C1and the inner light-emitting element12C2, the distance between the target object Ob and the outer light-emitting element12C1is shorter than the distance between the target object Ob and the inner light-emitting element12C2. Accordingly, irrespective of whether the target object Obis inside the outer light-emitting element12C1, the detection intensity in the photodetector30when the outer light-emitting element12C1is turned on is larger than the light-receiving intensity in the photodetector30when the inner light-emitting element12C2is turned on. In such a case, the inside/outside detector54stops detection of the coordinates of the target object Ob assuming that the target object Ob is outside the region surrounded by the circle with the radius r0. According to this method, in a case where the target object Ob is at least inside the region surrounded by the circle with the radius r0, the coordinates of the target object Ob can be detected with high precision.

In addition, in the present embodiment, the above inside/outside determination is performed in all of the first detection light source sections12A to the fourth detection light source sections12D. For this reason, even in a case where the target object Ob is located in the angular direction which intersects the X-axis direction and the Y-axis direction, it can be determined that the target object Ob is located either inside or outside the first detection light source section12A to the fourth detection light source section12D. Accordingly, the XY coordinates of the target object Ob can be detected with high precision.

Basic Detection Principle of Coordinates

FIGS. 4A and 4Bare explanatory views showing the basic principle of coordinate detection used in the optical position detecting device10to which the invention is applied.FIGS. 4A and 4Bare an explanatory view showing the relationship between the position of the target object Ob and the light-receiving intensity in the photodetector30, and an explanatory view showing that the light-emitting intensity of the detection light L2is adjusted so that the light-receiving intensities in the light detection section30become equal to each other.

In the optical position detecting device10of the present embodiment, as will be described below with reference toFIGS. 4A and 4BandFIGS. 5A and 5B, the position detecting section50obtains the ratio of the distance between one detection light source section12of the two detection light source sections12and the target object Ob and the distance between another detection light source section12and the target object Ob by the differential movement between the detection light source sections12or the differential movement between the detection light source section12and the reference light source12R, and detects the position of the target object Ob on the basis of this ratio.

Hereinafter, the basic principle when the X coordinate and Y coordinate of the target object Ob are detected from a plurality of results obtained by changing and differentially moving combinations of two detection light sources among the first detection light source section12A, the second detection light source section12B, the third detection light source section12C, and the fourth detection light source section12D on the basis of the light-receiving result of the photodetector30will be described.

In the optical position detecting device10of the present embodiment, the detection space10R is set on a first surface41side (space on the emitting side of the detection light L2from the light source unit11) of the translucent member40. Additionally, two detection light source sections12, for example, the first detection light source section12A and the third detection light source section12C, are separated from each other in the X-axis direction and Y-axis direction. For this reason, when the outer light-emitting element12A1of the first detection light source section12A is turned up and the detection light L2ais emitted, the detection light L2a, as shown inFIG. 4A, forms a first light intensity distribution L2Ga in which intensity decreases monotonously toward the other side from one side. Additionally, when the outer light-emitting element12C1of the third detection light source section12C is turned up and detection light L2cis emitted, the detection light L2cis transmitted through the translucent member40, and forms a second light intensity distribution L2Gc in which intensity increases monotonously on the first surface41side (detection space10R) toward the other side from one side.

In order to obtain the positional information on the target object Ob using the differential movement between the detection light L2aand L2c, first, as shown inFIG. 4A, the outer light-emitting element12A1of the first detection light source section12A is turned on, the outer light-emitting element12C1of the third detection light source section12C is turned off, and the first light intensity distribution L2Ga in which intensity decreases monotonously toward the other side from one side is formed. Additionally, the outer light-emitting element12A1of the first detection light source section12A is turned off, the outer light-emitting element12C1of the third detection light source section12C is turned on, and the second light intensity distribution L2Gc in which intensity increases monotonously toward the other side from one side is formed. Accordingly, when the target object Ob is arranged in the detection space10R, the detection light L2is reflected by the target object Ob, and a portion of the reflected light is detected by the photodetector30. In that case, the reflection intensity in the target object Ob is proportional to the intensity of the detection light L2at a place where the target object Ob is located, and the light-receiving intensity in the photodetector30is proportional to the reflection intensity in the target object Ob. Accordingly, the light-receiving intensity in the photodetector30has a value corresponding to the position of the target object Ob. Therefore, as shown inFIG. 4B, if the ratio of a driving current when the controlled variable (driving current) for the outer light-emitting element12A1of the first detection light source section12A is adjusted and a driving current when the controlled variable (driving current) for the outer light-emitting element12C1of the third detection light source section12C is adjusted, the ratio of the amounts of adjustment, or the like is used so that a detection value LGa in the photodetector30when the first light intensity distribution L2Ga is formed and a detection value LGc in the photodetector30when the second light intensity distribution L2Gc is formed become equal, it can be detected whether the target object Ob exists at any position between the outer light-emitting element12A1of the first detection light source section12A and the outer light-emitting element12C1of the third detection light source section12C within the XY plane.

More specifically, as shown inFIG. 4A, the first light intensity distribution L2Ga and the second light intensity distribution L2Gc are formed so that the light intensity distributions become opposite directions to each other. In this state, it can be seen that, if the detection values LGa and LGc in the photodetector30are equal to each other, the target object Ob is located at the center between the outer light-emitting element12A1of the first detection light source section12A and the outer light-emitting element12C1of the third detection light source section12C within the XY plane. On the other hand, in a case where the detection values LGa and LGc in the photodetector30are different from each other, as shown inFIG. 4B, the first light intensity distribution L2Ga and the second light intensity distribution L2Gc are sequentially formed again by adjusting the controlled variable (driving current) for the outer light-emitting element12A1of the first detection light source section12A and the outer light-emitting element12C1of the third detection light source section12C so that the detection values LGa and LGc become equal to each other. As a result, if the detection values LGa and LGc in the photodetector30become equal to each other, and the ratio of a driving current for the outer light-emitting element12A1of the first detection light source section12A and a driving current for the outer light-emitting element12C1of the third detection light source section12C at that time is used, it can be detected whether the target object Ob exists at any position between the outer light-emitting element12A1of the first detection light source section12A and the outer light-emitting element12C1of the third detection light source section12C within the XY plane.

When this detection principle is mathematically described using an optical path function, this is as follows. First, in the above differential movement, when the driving current for the outer light-emitting element12A1of the first detection light source section12A when the light-receiving intensities in the photodetector30become equal to each other is defined as IA, the driving current for the outer light-emitting element12C1of the third detection light source section12C is defined as IC, and the ratio of a distance function which leads to the photodetector30via the target object Ob from the outer light-emitting element12A1of the first detection light source section12A and a distance function which leads to the photodetector30via the target object Ob from the outer light-emitting element12C1of the third detection light source section12C is defined as PAC, the ratio PACis basically obtained according to the following expression:
PAC=IC/IA.
Accordingly, it can be seen that the target object Ob position is located on an equal ratio line passing through a position obtained by dividing a line which connects the outer light-emitting element12A1of the first detection light source section12A and the outer light-emitting element12C1of the third detection light source section12C by a predetermined ratio.

This model will be mathematically described. First, respective parameters are defined as follows.

T=Reflectivity of target object Ob

At=Distance function when detection light L2emitted from outer light-emitting element12A1of first detection light source section12A is reflected by target object Ob and reaches photodetector30

A=Detection intensity of photodetector30when outer light-emitting element12A1of first detection light source section12A is turned up in a state where target object Ob exists in detection space10R.

Ct=Distance function when detection light L2emitted from outer light-emitting element12C1of third light source section12C is reflected by target object Ob and reaches photodetector30

C=Detection intensity of photodetector30when outer light-emitting element12C1of third detection light source section12C is turned up in a state where target object Ob exists in detection space10R.

In addition, although the emission intensity of the outer light-emitting element12A1of the first detection light source section12A and the emission intensity of the outer light-emitting element12C1of the third detection light source section12C are expressed by the product of a driving current and an emission coefficient, the emission coefficient is set to 1 in the following description.

Additionally, when the above-mentioned differential movement is performed in a state where the target object Ob exists in the detection space10R, the following relationships are obtained.
A=T×At×IA+Environmental light  (1)
C=T×Ct×IC+Environmental light  (2)

Here, since the detection intensity of the photodetector30is equal during differential movement, the following expressions are derived from Expressions (1) and (2).
T×At×IA+Environmental light=T×Ct×IC+Environmental light
T×At×IA=T×Ct×IC(3)

Additionally, since the ratio PACof the distance functions Atand Ctis defined by the following expression:
PAC=At/Ct(4),
the ratio of the distance function PACis expressed as shown below from Expressions (3) and (4):
PAC=IC/IA(5).
In this Expression (5), the item of the environmental light and the item of the reflectivity of the target object Ob do not exist. Therefore, the environmental light and the reflectivity of the target object Ob do not influence the ratio PACof the optical path coefficients Atand Ct. In addition, the correction for offsetting the influence or the like of the detection light L2which has been incident without being reflected by the target object Ob may be performed on the above mathematical model.

Here, a light source used in the detection light source section12is a point light source, and the optical intensity thereof at a certain point is inversely proportional to the square of a distance from the light source. Accordingly, the ratio of the separation distance P1between the outer light-emitting element12A1of the first detection light source section12A and the target object Ob and the separation distance P2between the outer light-emitting element12C1of the third detection light source section12C and the target object Ob is obtained according to the following expression:
PAC=(P1)2:(P2)2.
Therefore, it can be seen that the target object Ob position is located on an equal ratio line passing through a position obtained by dividing an imaginary line which connects the outer light-emitting element12A1of the first detection light source section12A and the outer light-emitting element12C1of the third detection light source section12C in P1:P2.

Similarly, if the outer light-emitting element12B1and the outer light-emitting element12D1are differentially moved and the ratio of the distance between the outer light-emitting element12B1and the target object Ob and the distance between the outer light-emitting element12D1and the target object Ob is obtained, it can be seen that the target object Ob exists on an equal ratio line passing through a position which divides an imaginary line which connects the outer light-emitting element12B1and the outer light-emitting element12D1by a predetermined ratio. Therefore, the X coordinate and Y coordinate of the target object Ob can be detected. In addition, the above method is a method of geometrically describing the principle adopted in the present embodiment. In practice, calculation is performed using the obtained data.

If the inside/outside determination described with reference toFIGS. 3A to 3Eis performed in detecting the X coordinate and the Y coordinate in this way, when an imaginary line which connects the outer light-emitting element12A1and the outer light-emitting element12C1is divided, and when an imaginary line which connects the outer light-emitting element12B1and the outer light-emitting element12D1is divided, proper division can be performed if it is known whether the target object Ob is located inside or outside the first detection light source section12A to the fourth detection light source section12D. Therefore, the X coordinate and Y coordinate of the target object Ob can be detected with high precision.

Differential Movement Between Reference Light Lr and Detection Light L2

FIGS. 5A and 5Bare explanatory views showing a principle that the position of a target object Ob is detected using the differential movement between the reference light Lr and the detection light L2, in the optical position detecting device10to which the invention is applied, andFIGS. 5A and 5Bare an explanatory view showing the relationship between the distance from the detection light source section12to the target object Ob and the light-receiving intensity of the detection light L2or the like, and an explanatory view showing an aspect after a driving current to a light source is adjusted.

In the optical position detecting device10of the present embodiment, the differential movement between the detection light L2aand the reference light Lr and the differential movement between the detection light L2cand the reference light Lr are used instead of the direct differential movement between the detection light L2aand the detection light L2c, and eventually the same result as the principle described with reference toFIGS. 4A and 4Bis derived. Here, the differential movement between the detection light L2aand the reference light Lr and the differential movement between the detection light L2cand the reference light Lr are executed as follows.

As shown inFIG. 5A, in a state where the target object Ob exists in the detection space10R, the distance to the target object Ob from the outer light-emitting element12A1of the first detection light source section12A, and the light-receiving intensity Daof the detection light L2ain the photodetector30vary monotonously as shown by a solid line SA. On the other hand, the detection intensity in the photodetector30of the reference light Lr emitted from the reference light source12R is constant irrespective of the position of the target object Ob as shown by a solid line SR. Accordingly, the light-receiving intensity Daof the detection light L2ain the photodetector30and the detection intensity Drof the reference light Lr in the photodetector30are different from each other.

Next, as shown inFIG. 5B, at least one of a driving current for the outer light-emitting element12A1of the first detection light source section12A and a driving current for the reference light source12R is adjusted, and the light-receiving intensity Daof the detection light L2ain the photodetector30and the detection intensity Drin the photodetector30of the reference light Lr are made to coincide with each other. Such a differential movement is performed between the reference light Lr and the detection light L2aand is performed between the reference light Lr and the detection light L2c. Accordingly, it is possible to obtain the ratio of a driving current for the outer light-emitting element12A1of the first detection light source section12A and a driving current for the outer light-emitting element12C1of the third detection light source section12C when a detection result of the detection light L2aor L2c(detection light L3aor L3creflected by the target object Ob) in the photodetector30and a detection result of the reference light Lr in the photodetector30become equal each other. Therefore, it can be detected whether the target object Ob exists in any position between the first detection light source section12A and the third detection light source section12C.

When the above detection principle is mathematically described using an optical path function, this as follows. First, respective parameters are defined as follows.

T=Reflectivity of target object Ob

At=Distance function when detection light L2emitted from outer light-emitting element12A1of first detection light source section12A is reflected by target object Ob and reaches photodetector30

A=Detection intensity of photodetector30when outer light-emitting element12A1of first detection light source section12A is turned up in a state where target object Ob exists in detection space10R.

Ct=Distance function when detection light L2emitted from outer light-emitting element12C1of third detection light source section12C is reflected by target object Ob and reaches photodetector30

C=Detection intensity of photodetector30when outer light-emitting element12C1of third detection light source section12C is turned up in a state where target object Ob exists in detection space10R.

Rs=Optical path coefficient from reference light source12R to photodetector30

R=Detection intensity of photodetector30when only reference light source12R is turned up.

In addition, although the emission intensity of the outer light-emitting element12A1of the first detection light source section12A, the emission intensity of the outer light-emitting element12C1of the third detection light source section12C, and the emission intensity of the reference light source12R are expressed by the product of a driving current and an emission coefficient, the emission coefficient is set to 1 in the following description. Additionally, when the light-receiving intensities in the photodetector30become equal to each other in the above differential movement, the driving current for the outer light-emitting element12A1of the first detection light source section12A is defined as IA, the driving current for the outer light-emitting element12C1of the third detection light source section12C is defined as IC, and the driving current for the reference light source12R is defined as IR. Additionally, it is assumed that the detection intensity of the photodetector30when only the reference light source12R is turned up during differential movement is the same in the differential movement from the outer light-emitting element12A1of the first detection light source section12A and in the differential movement from the outer light-emitting element12C1of the third detection light source section12C.

Additionally, when the above-mentioned differential movement is performed in a state where the target object Ob exists in the detection space10R, the following relationships are obtained.
A=T×At×IA+Environmental light  (6)
C=T×Ct×IC+Environmental light  (7)
R=RS×IR+Environmental light  (8)

Here, since the detection intensity of the photodetector30is equal during differential movement, the following expressions are derived from Expressions (6) and (8):
T×At×IA+Environmental light=RS×IR+Environmental light
T×At×IA=RS×IR
T×At=RS×IR/IA(9)
and, the following expressions are derived from expressions (7) and (8):
T×Ct×IC+Environmental light=RS×IR+Environmental light
T×Ct×IC=RS×IR
T×Ct=RS×IR/IC(10).
Additionally, since the ratio PACof the distance functions Atand Ctis defined by the following expression:
PAC=At/Ct(11),
the ratio of the distance function PACis expressed as shown below from Expressions (9) and (10):
PAC=IC/IA(12).
In this Expression (12), the item of the environmental light and the item of the reflectivity of the target object Ob do not exist. Therefore, the environmental light and the reflectivity of the target object Ob do not influence the ratio PACof the optical path coefficients Atand Ct. In addition, the correction for offsetting the influence or the like of the detection light L2which has been incident without being reflected by the target object Ob may be performed on the above mathematical model. Additionally, even when the detection intensity of the photodetector30when only the reference light source12R is turned up is set to a different value in the differential movement from the outer light-emitting element12A1of the first detection light source section12A, and the differential movement from the outer light-emitting element12C1of the third detection light source section12C, the same principle is basically established.

Here, a light source used in the detection light source section12is a point light source, and the optical intensity thereof at a certain point is inversely proportional to the square of a distance from the light source. Accordingly, the ratio of the separation distance P1between the outer light-emitting element12A1of the first detection light source section12A and the target object Ob and the separation distance P2between the outer light-emitting element12C1of the third detection light source section12C and the target object Ob is obtained according to the following expression:
PAC=(P1)2:(P2)2.
Therefore, it can be seen that the target object Ob position is located on an equal ratio line passing through a position obtained by dividing an imaginary line which connects the outer light-emitting element12A1of the first detection light source section12A and the outer light-emitting element12C1of the third detection light source section12C in P1:P2.

Similarly, if the ratio of the distance between the outer light-emitting element12B1and the target object Ob and the distance between the outer light-emitting element12D1and the target object Ob is obtained using the differential movement between the outer light-emitting element12B1and the reference light source12R and the differential movement between the outer light-emitting element12D1and the reference light source12R, it can be seen that the target object Ob exists on an equal ratio line passing through a position which divides an imaginary line which connects the outer light-emitting element12B1and the outer light-emitting element12D1by a predetermined ratio. Therefore, the XY coordinates of the target object Ob can be detected.

If the inside/outside determination described with reference toFIGS. 3A to 3Eis performed in detecting the X coordinate and the Y coordinate in this way, when an imaginary line which connects the outer light-emitting element12A1and the outer light-emitting element12C1is divided, and when an imaginary line which connects the outer light-emitting element12B1and the outer light-emitting element12D1is divided, proper division can be performed if it is known whether the target object Ob is located inside or outside the first detection light source section12A to the fourth detection light source section12D. Therefore, the X coordinate and Y coordinate of the target object Ob can be detected with high precision.

Configuration Example of Position Detecting Section50for Differential Movement

FIGS. 6A and 6Bare explanatory views showing the contents of processing performed by the position detecting section50, in the optical position detecting device10to which the invention is applied.

In carrying out the above differential movement, it is possible to adopt a configuration in which processing is performed by using a microprocessor unit (MPU) as the position detecting section50, and thereby, executing predetermined software (operation program). Additionally, it is also possible to adopt a configuration in which processing is performed in a signal processor using hardware, such as a logical circuit, as will be described below with reference toFIGS. 6A and 6B. In addition, although the differential movement described with reference toFIGS. 5A and 5Bis shown inFIGS. 6A and 6B, if the reference light source12R is replaced with the second detection light source section12B, the invention can be applied to the differential movement described with reference toFIGS. 4A and 4B.

As shown inFIG. 6A, in the optical position detecting device10of the present embodiment, the light source driving circuit140applies a driving pulse of a predetermined current value to the first detection light source section12A via a variable resistance111, and applies a driving pulse of a predetermined current value to the reference light source12R via a variable resistance112and an inverting circuit113. For this reason, since reversed-phase driving pulses are applied to the first detection light source section12A and the reference light source12R, the first detection light source section12A and the reference light source12R are alternately turned on. Also, when the first detection light source section12A is turned on, the light reflected by the target object Ob in the detection light L2ais received in the photodetector30, and when the reference light source12R is turned up, the reference light Lr is received in the photodetector30. In the optical intensity signal generation circuit150, a resistor30rof about 1 kΩ is electrically connected in series to the photodetector30, and a bias voltage Vb is applied to both ends thereof.

In the optical intensity signal generation circuit150, the position detecting section50is electrically connected to a connection point Q1between the photodetector30and the resistor30r. A detection signal Vc output from the connection point Q1between the photodetector30and the resistor30ris expressed by the following expression:
Vc=V30/(V30+resistance value of resistor 30r)

V30: equivalent resistance value of photodetector30. Accordingly, when a case where the environmental light Lc does not enter the photodetector30is compared with a case where the environmental light Lc enters the photodetector30, the level and amplitude of the detection signal Vc become large in the case where the environmental light Lc enters the photodetector30.

The position detecting section50generally includes a signal extraction circuit190for position detection, a signal separation circuit170for position detection, and an emission intensity compensation command circuit180. The signal extraction circuit190for position detection includes a filter192of a capacitor of about 1 nF, and the filter192functions as a high-pass filter which removes a direct-current component from a signal output from the connection point Q1between the photodetector30and the resistor30r. For this reason, only a position detection signal Vd by the photodetector30is extracted from the detection signal Vc output from the connection point Q1between the photodetector30and the resistor30rby the filter192. That is, since it can be regarded that the detection light L2aand the reference light Lr are modulated, whereas the environmental light Lc has an intensity being constant within a certain period, a low-frequency component or direct-current component resulting from the environmental light Lc is removed by the filter192.

Additionally, the signal extraction circuit190for position detection has an adder circuit193including a feedback resister194of about 220 kΩ in a subsequent stage of the filter192, and the position detection signal Vd extracted by the filter192is output to the signal separation circuit170for position detection as a position detection signal Vs on which a voltage V/2 of ½ times the bias voltage Vb is overlapped.

The signal separation circuit170for position detection includes a switch171which performs a switching operation in synchronization with a driving pulse applied to the first detection light source section12A, a comparator172, and a capacitor173which is electrically connected to an input line of the comparator172. For this reason, when the position detection signal Vs is input to the signal separation circuit170for position detection, an effective value Vea of the position detection signal Vs when the first detection light source section12A is turned up and an effective value Veb of the position detection signal Vs when the reference light source12R is turned up are alternately output to the emission intensity compensation command circuit180from the signal separation circuit170for position detection.

The emission intensity compensation command circuit180compares the effective values Vea and Veb with each other, performs the processing shown inFIG. 6B, and outputs a control signal Vf to the light source driving circuit140so that the effective value Vea of the position detection signal Vs and the effective value Veb of the position detection signal Vs become the same level. That is, the emission intensity compensation command circuit180compares the effective value Vea of the position detection signal Vs with the effective value Veb of the position detection signal Vs, and maintains the present driving conditions in a case where the effective values are equal to each other. On the other hand, in a case where the effective value Vea of the position detection signal Vs is lower than the effective value Veb of the position detection signal Vs, the emission intensity compensation command circuit180reduces the resistance value of the variable resistance111, and increases the quantity of the light emitted from the first detection light source section12A. Additionally, in a case where the effective value Veb of the position detection signal Vs is lower than the effective value Vea of the position detection signal Vs, the emission intensity compensation command circuit180reduces the resistance value of the variable resistance112, and increases the quantity of the light emitted from the reference light source12R.

In this way, in the optical position detecting device10, the controlled variables (driving currents) of the first detection light source section12A and the reference light source12R are controlled by the emission intensity compensation command circuit180of the position detecting section50so that the amounts of detection by the photodetector30during the turn-on operation of the first detection light source and the turn-on operation of the reference light source become equal to each other. Accordingly, information on the driving currents for the first detection light source section12A and the reference light source section12R so that the amounts of detection by the photodetector30during the turn-on operation of the first detection light source and the turn-on operation of the reference light source become equal to each other exist in the emission intensity compensation command circuit180, and this information is output to the position detecting section50as a position detection signal Vg.

The same processing is performed even between the second detection light source section12B, and the reference light source12R, and the signal Vg for position detection which is output from the emission intensity compensation command circuit180is information on the driving currents for the second detection light source section12B and the reference light source section12R so that the amounts of detection by the photodetector30during the turn-on operation of the second detection light source section and the turn-on operation of the reference light source become equal to each other.

Detection of Z Coordinate

In the optical position detecting device10of the present embodiment, when the first detection light source section12A to the fourth detection light source section12D are simultaneously turned on, a light intensity distribution for Z coordinate detection in which intensity decreases monotonously in the normal direction to the first surface41are formed on the first surface41side (detection space10R) of the translucent member40. In this light intensity distribution for Z coordinate detection, intensity decreases monotonously as it separates from the first surface41of the translucent member40. Accordingly, in the Z coordinate detector53of the position detecting section50, the Z coordinate of the target object Ob can be detected on the basis of the difference or ratio of the detection values in the photodetector30when the reference light source12R, and the first detection light source section12A to the fourth detection light source section12D are alternately turned on. Additionally, in the Z coordinate detector53of the position detecting section50, the Z coordinate of the target object Ob can be detected on the basis of the difference or ratio of the driving current for the reference light source12R and the driving currents for the first detection light source section12A to the fourth detection light source section12D when the detection values in the photodetector30when the reference light source12R and the first detection light source section12A to the fourth detection light source section12D are alternately turned on become equal to each other.

MAIN EFFECTS OF PRESENT EMBODIMENT

As described above, in the optical position detecting device10of the present embodiment, the light source driving section14turns on the plurality of detection light source sections12sequentially, and the photodetector30receives the detection light L3reflected by the target object Ob during that time. Accordingly, if a detection result in the photodetector30is directly used, or a driving current when the two detection light source sections12are differentially moved via the photodetector30is used, the position detecting section50can detect the position of the target object Ob. Here, as seen from the detection space10R, the photodetector30is located inside the plurality of detection light source sections12, the plurality of detection light source sections12includes the outer light-emitting elements12A1to12D1and the inner light-emitting elements12A2to12D2, respectively. Accordingly, the position detecting section50can determine whether the target object Obis located either outside or inside the detection light source sections on the basis of comparison results between the light-receiving intensities in the photodetector30when the outer light-emitting elements12A1to12D1are turned on and the light-receiving intensities in the photodetector30when the inner light-emitting elements12A2to12D2are turned on. For this reason, when the ratio of the distance between one detection light source section12of the two detection light source sections12and the target object Ob and the distance between the other detection light source section12and the target object Ob is obtained, the distance between the two detection light source sections12may be internally divided to specify the position of the target object Ob. However, there is no doubt whether the distance between the two detection light source sections12may be externally divided to specify the position of the target object Ob. Therefore, the position of the target object Ob can be accurately detected.

Additionally, in the present embodiment, since the differential movement in the two detection light source sections12or the differential movement between the detection light source section12and the reference light source12R is used, the influence of environmental light or the like can be automatically corrected.

Moreover, since the detection light L2is infrared light, the detection light is not viewed. Accordingly, the optical position detecting device10can be used for various apparatuses, so as not to hinder the display even in a case where the optical position detecting device10of the present embodiment is applied to a display apparatus.

OTHER EMBODIMENTS

Although the outer light-emitting elements12A1to12D1are turned on when a differential movement is performed in the above embodiment, the inner light-emitting elements12A2to12D2may be turned on. Additionally, the outer light-emitting elements12A1to12D1and the inner light-emitting elements12A2to12D2may be turned on.

Example of Use of Optical Position Detecting Device10

A robot hand unit using the optical position detecting device10to which the invention is applied as a tactile sensor will be described with reference toFIGS. 7A and 7B.FIGS. 7A and 7Bare explanatory views of a robot arm provided at the hand unit using the optical position detecting device10to which the invention is applied as a tactile sensor, andFIGS. 7A and 7Bare an explanatory view of the overall robot arm, and an explanatory view of the hand unit.

The robot arm200shown inFIG. 7Ais an apparatus which performs supply, extraction, or the like of workpieces or tools with respect to a numerically controlled machine tool, and includes a strut220erected from a base290, and an arm210. In the present embodiment, the arm210includes a first arm portion230coupled with a tip portion of the strut220via a first joint260, and a second arm portion240coupled with a tip portion of the first arm portion230via a second joint270. The strut220is rotatable around an axis H1perpendicular to the base290, the first arm portion230is rotatable around an axis H2by the first joint260at the tip portion of the strut220, and the second arm portion240is rotatable around an axis H3by the second joint270at the tip portion of the first arm portion230. A hand450of the hand unit400is coupled with the tip portion of the second arm portion240, and the hand450is rotatable around an axis H4of the second arm portion240.

As shown inFIG. 7B, the hand unit400has the hand450including a plurality of grip claws410(gripper), and the hand450includes a disk-shaped grip claw support420holding the roots of the plurality of grip claws410. In the present embodiment, the hand450includes a first grip claw410A and a second grip claw410B as the plurality of grip claws410. Both of the two grip claws410are movable in a direction in which the grip claws are separated from each other and in a direction in which the grip claws approach each other, as shown by an arrow H4.

In the robot arm200configured in this way, when the target object Ob is gripped, the two grip claws410move in the direction in which the grip claws approach each other, thereby gripping the target object Ob after the strut220, the first arm portion230, and the second arm portion240rotate in a predetermined direction to make the hand450approach the target object Ob (a workpiece).

Here, the inner surface of each grip claw410which comes in contact with the target object Ob when the target object Ob (the workpiece) is gripped includes the first surface of the translucent member40of the optical position detecting device10described in the above embodiment. Accordingly, when the grip claws410grip the target object Ob, the optical position detecting device10detects the relative position or position of the target object Ob and the grip claw410, and this detection result is fed back to a driving controller of the grip claws410. Therefore, the grip claws410can be made to approach the target object Ob at high speed, and an increase in the speed of a workpiece gripping operation can be realized.