JPH0675686A - Optical position measuring instrument - Google Patents

Abstract

(57) [Abstract] [Purpose] To eliminate the mechanical error of the optical position measuring device and improve the measurement accuracy. The optical position measuring apparatus includes light beam emitting means 1R and 1L for emitting a light beam, deflecting means 2R and 2L for deflecting the light beam, and positions where the deflected light beams VR and VL are designated. Position indicating means 4 for detecting passage
And a deflection amount detecting means for measuring the deflection amounts of the light beams VR and VL in synchronization with the detection. The deflection amount detecting means is composed of light beam detecting means 3R, 3L which are respectively interposed between the deflecting means 2R, 2L and the position indicating means 4 and optically detect the directions of the light beams VR, VL directly. ing.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an optical position measuring device. Specifically, the present invention relates to a coordinate input device or digitizer for inputting a figure or the like by designating two-dimensional coordinates.

[0002]

2. Description of the Related Art Conventionally, as an optical position measuring device,
A triangulation method using a light beam is known,
For example, it is disclosed in JP-A-3-5805. In order to clarify the background of the present invention, this conventional example will be briefly described with reference to FIG. This conventional device has a light reflection type cursor 101. The cursor 101 is movably arranged along the XY coordinate plane 102 for designating the coordinates to be input. The central axis P of the cursor 101 is aligned with a predetermined point in order to specify a predetermined coordinate. The light beam along the optical path toward the central axis of the cursor 101 is reflected by the cylindrical reflecting surface of the cursor 101 and moves backward along the same optical path. A pair of left and right light source units L and R are mounted on the upper edge of the coordinate plane 102 along the X axis. The light source unit R on the right side deflects the light beam VR while angularly scanning it along the coordinate plane 102, and when the light beam VR coincides with the central axis P of the cursor 101, the light beam is reflected and moves backward. It receives VR and generates a detection signal. The left light source unit L is arranged along the X-axis with a distance d from the right light source unit R, and similarly deflects the light beam VL while angularly scanning along the coordinate plane 102. . When the light beam VL coincides with the central axis P of the cursor 101, the light beam VL is reflected and moves backward.
Are received by the same light source unit L and a detection signal is output.

This conventional device is a pair of light source units R and L.
Has a calculation unit 103 connected to. The calculation unit 103 calculates the angle θR formed by the backward light beam VR and the X axis based on the output signal sent from the light source unit R on the right side, and goes backward based on the output signal sent from the light source unit L on the left side. The angle θL formed by the light beam VL and the X axis is calculated. Further, using the calculated angle values θR and θL and the distance d between the pair of light source units, the cursor 10 is operated according to the principle of triangulation.
Calculate the coordinates specified by 1.

FIG. 7 is a diagram showing an optical configuration of the light source unit R. The other light source units L also have the same configuration. The light source unit R receives a detection signal by receiving a laser light source 119 that emits a light beam along the X-axis, a rotary reflecting mirror 120 that rotates at a constant angular velocity to angularly deflect the light beam, and a backward light beam. It has a light receiving element 121 for generating light.
As is apparent from the figure, the light beam emitted from the laser light source 119 passes through the half mirror 122 and passes through the rotary reflecting mirror 12.
Go to the center of rotation of 0. Here, the light beam is deflected at a constant angular velocity, and as described above, it is reflected when it coincides with the central axis of the cursor, moves backward, returns to the rotary reflecting mirror 120, and further reflects there, and goes to the half mirror 122. The backward light beam is separated by the half mirror 122, and is received by the light receiving element 121 via the filter. The light receiving element 121 outputs the detection pulse G in synchronization with the light receiving timing.

The rotary reflecting mirror 120 is rotated at a constant angular velocity by a drive circuit 123. The drive circuit 123 outputs the timing pulse F every one rotation cycle of the rotary reflecting mirror 120. The timing pulse F and the detection pulse G are input to the processing circuit 124, and a predetermined output signal is obtained. Since this output signal is output according to the time interval in which the detection pulse G is generated with reference to the timing pulse F,
The above-mentioned angle value θR is represented on the assumption that the rotary reflecting mirror 120 is rotating at a constant angular velocity.

[0006]

FIG. 8 is a schematic timing chart showing the relationship between the timing pulse F and the detection pulse G. The timing pulse F is the rotary reflecting mirror 1.
Each time 20 rotates once in a predetermined cycle T, it is generated at a predetermined timing, for example, at a timing when the normal line of the rotary reflecting mirror 120 is parallel to the light beam from the laser light source 119. On the other hand, the detection pulse G has a large peak and a subsequent small peak. The large peak occurs in the state where the rotary reflecting mirror 120 is positioned perpendicular to the light beam from the laser light source 119, is synchronized with the timing pulse F, and is independent of the backward light beam from the cursor 101. The subsequent small peak is synchronized with the timing at which the backward light beam from the cursor 101 is received by the deflection scanning of the light beam. If it occurs t hours after the large peak, this time t is proportional to the angle value θR to be obtained. Are related to each other. When expressed by a mathematical expression, θR = 4π × t
It becomes like / T.

The above-described measurement of the angle value θR is based on the assumption that the rotary reflecting mirror rotates at a constant angular velocity. However, in reality, there are problems or problems that the angular velocity fluctuates due to various factors and the measurement accuracy of the angle value θR is poor. In other words, the motor that is the drive source of the rotary reflector,
There is a drawback in that the mechanical accuracy of the connection mechanism between the motor and the rotary reflecting mirror and the bearing directly affects the measurement accuracy. Therefore, in order to improve the measurement accuracy, a motor with less uneven rotation and a rotary reflecting mirror accurately connected to a frictionless bearing are required. Therefore, for example, an extremely expensive air bearing mechanism or the like is required, and there is a problem that the manufacturing cost becomes very high.

An optical position measuring device which does not use moving parts such as a motor and a rotary reflecting mirror is also known, and is disclosed in, for example, Japanese Patent Laid-Open No. 3-196326. For reference, this conventional example will be briefly described with reference to FIG. A light emitting element 202 is attached to the tip of an input pen 201 for position designation. On the other hand, the light receiving unit 203 includes a pair of light spot position detection elements 204, which are arranged with a predetermined distance therebetween.
It is equipped with 205. The point emission from the input pen 201 is imaged on the corresponding light spot position detecting element via the condenser lenses 206 and 207, respectively. According to the principle of triangulation, the coordinate of the designated position is calculated by the calculation unit 208 based on the detected spot position. However,
In this conventional example, if the distance of the input pen 201 with respect to the light receiving unit 203 changes, there is a drawback that a large error occurs in the measurement result of the designated position because the focused light spot is not imaged. Therefore, in principle, the structure using the light beam deflection method is superior from the viewpoint of accuracy.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to directly influence the position measurement accuracy by the mechanical accuracy of mechanical parts such as a motor and a rotary reflecting mirror in an optical position measuring device using a light beam deflection system. The objective is to provide a light beam deflection amount detection method. The following measures have been taken in order to achieve this object. That is, a light beam emitting means for emitting a light beam, a deflecting means for deflecting the light beam, a position indicating means for detecting that the deflected light beam has passed a designated position, and a synchronizing means for detecting the position. In an optical position measuring device comprising a deflection amount detecting means for detecting the deflection amount of the light beam, the deflection amount detecting means is interposed between the deflecting means and the position indicating means and optically directs the light beam direction. It is characterized by comprising a light beam detecting means for detecting.

Preferably, the light beam detection means detects the spot position of the light beam on the front side, and the second light spot position detection means on the rear side detects the spot position of the same light beam. It is characterized by consisting of a pair with. Further, the light beam detecting means is a CC
It is characterized by comprising a D linear image sensor, a MOS linear image sensor or a PSD. Furthermore, by providing a pair of light source units, each consisting of a light beam emitting means, a deflecting means, and a light beam detecting means, on the left and right sides, it becomes possible to detect the two-dimensional position designated by the position indicating means.

[0011]

In the present invention, the light beam detecting means is interposed between the deflecting means and the position indicating means. The light beam detecting means optically directly detects the light beam direction. Therefore, even if a mechanical error is included in the mechanical components such as the rotary reflecting mirror, the motor, or the bearing that constitute the deflecting means, the detection accuracy of the light beam direction is not affected at all. Therefore, the deflection angle of the light beam can be obtained with extremely high accuracy, and the specified position can be precisely specified based on the principle of triangulation. On the other hand, since the mechanical accuracy of the deflecting means has a considerable allowance, the cost of parts can be kept low.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic block diagram showing the basic configuration of an optical position measuring device according to the present invention.
The apparatus according to the present invention comprises at least one light source unit. In this embodiment, a pair of left and right light source units L and R are fixedly arranged in order to obtain the two-dimensional coordinates of a designated position based on the principle of triangulation. ing. When only the azimuth of the designated position is detected, one light source unit may be used. Further, when obtaining the three-dimensional coordinates of the designated position, at least three light source units are used. The pair of left and right light source units L and R basically have the same structure. For example, the light source unit R on the right side includes a light beam emitting means 1R for emitting a light beam, a deflecting means 2R for deflecting the light beam, and a deflection amount detecting means 3R for detecting the deflection amount of the light beam. . In addition, when specifying the left and right light source units individually, R is assigned to each reference number.
Alternatively, the reference symbol L is also shown, but it may be omitted if not particularly necessary.

The present apparatus further includes a position indicating means 4 for inputting and designating a desired position within a given measurement area 5. The deflection means 2 included in each light source unit angularly deflects and scans the light beam in a range that covers the measurement area 5. The position indicating means 4 has a stylus or pen shape that can be easily operated manually, and has a function of detecting that the deflected light beams VR and VL have passed a designated position. For example, a retroreflective surface is provided as in the conventional example shown in FIG. 6, and the incident light beams VR and VL are reflected and travel back to the light source unit side. Alternatively, instead of this, a light receiving element is used to generate the light beams VR, V.
The incident timing of L may be detected and fed back to the light source unit side wirelessly or by wire.

As a feature of the present invention, the above-mentioned deflection amount detecting means 3 is interposed between the deflecting means 2 and the position indicating means 4 and optically detects the light beams VR and VL directly. The means 3R and 3L. A calculator 6 is connected to the pair of light beam detecting means 3R and 3L.

Next, the operation of the optical position measuring device will be described. The light beam emitted from the light beam emitting means 1 is deflected by the deflecting means 2 and angularly scans the measurement region 5.
In synchronization with the time when the scanning light beams VR and VL are detected by the position indicating means 4, the respective light beam detecting means 3R and 3R.
L detects and measures the directions of the corresponding light beams VR, VL. The calculation unit 6 calculates the two-dimensional absolute coordinates of the designated position based on the measured angle data of the light beam direction according to the principle of triangulation.

Next, a specific structure of the light source unit will be described with reference to FIG. The light beam emitting means 1 is composed of, for example, a laser diode or the like that continuously emits a laser beam. The light beam detecting means 3 includes a front light spot position detecting means 31A for detecting the spot position of the light beam on the front side and a rear light spot position detecting means 31B for detecting the spot position of the same light beam on the rear side. Contains a pair. Each light spot position detecting means 31A, 31B
Is composed of a CCD linear image sensor, a MOS linear image sensor, a PSD, or the like. The CCD linear image sensor is, for example, a NEC pixel data rate 40 MHz 5000 pixel linear image sensor μP.
D35H71D can be used. As the PSD, for example, a one-dimensional long light receiving surface type PSD manufactured by Hamamatsu Photonics
S1352 or the like can be used. This CCD linear image sensor has a resolution of 1/5000 and can detect the spot position of the light beam with extremely high accuracy.
Further, the PSD can detect the spot position of the light beam in an analog manner based on the pair of differential outputs. Although it is inferior in accuracy to the CCD linear image sensor and the MOS linear image sensor, it is advantageous in cost.

FIG. 3 is a side view showing a concrete structure of the light source unit. The deflecting means 2 is composed of a rotary reflecting mirror 21 and a motor 22. The rotary reflecting mirror 21 is connected to a motor 22 via a shaft and is rotationally driven. Unlike the prior art, it is not necessary to control the rotation speed precisely and constantly, and relatively inexpensive parts can be used. Beam splitting means 32A and 32B such as half mirrors are serially inserted in the optical path of the deflected and scanned light beam.
Beam splitting means 3 on the front side near the rotary reflecting mirror 21
2A separates a part of the light beam from the optical path, and irradiates the corresponding front-side light spot position detection means 31A with the light spot. The separated light spot moves along the linear light receiving surface 33A of the pre-stage light spot position detecting means 31A in accordance with the deflection scanning of the light beam. Similarly, a light beam spot is separated from the same light beam by the post-stage beam splitting means 32B located at a position far from the rotary reflecting mirror 21, and the corresponding light receiving surface 33B is irradiated with the light spot.

In the concrete examples shown in FIGS. 2 and 3,
Although the light beam detecting means 3 comprises a pair of front and rear light spot position detecting means, the present invention is not necessarily limited to this. For example, it is possible to measure the light beam direction by arranging one light spot position detecting means with reference to the rotation axis of the rotary reflecting mirror 2.
However, using a pair of light spot position detecting means is superior in terms of accuracy. However, it is disadvantageous in terms of cost. Further, in the above-described specific example, the light spots are separated via the beam splitting means 32A and 32B.
The present invention is not necessarily limited to such a configuration.
For example, the light spot position detecting means having a relatively high transmittance may be directly interposed in the optical path of the light beam.

Next, the procedure for calculating the coordinates of the designated position will be described with reference to FIG. The measurement area 5 is given an XY coordinate system. The two-dimensional coordinates of the position P input and designated by the position indicating means are given by (X, Y). The light source unit on the right side is installed at a specific point PR (D, 0) on the X axis, and the light source unit on the left side is installed at another specific point PL (-D, 0) on the X axis. Both light source units are arranged symmetrically with respect to the Y axis, and the normal line SR of the light beam detecting means 3R on the right side and the normal line SL of the light beam detecting means 3L on the left side intersect each other at a specific point PO on the Y axis. There is. or,
The intersection angles φ between the normal lines SR and SL and the X axis are set to have the same inclination.

The direction of the right-side light beam VR that coincides with the designated position P is represented by an angle of deviation α with respect to the corresponding normal line SR. The argument α is given a positive or negative sign with reference to the normal line SR. Similarly, the deflection angle of the light beam VL that coincides with the designated position P is represented by β. The light beams VR and VL are represented by the following linear equations, respectively.

## EQU1 ## Y = tan (φ + α) X-tan (φ + α) D

## EQU00002 ## Y = -tan (.phi. +. Beta.) X-tan (.phi. +. Beta.) D When these two mathematical expressions are solved as a two-dimensional simultaneous equation concerning X and Y, the designated positions are given as shown in the following mathematical expressions 3 and 4. The X and Y coordinates of P are calculated.

X = D {tan (φ + α) −tan (φ +
β)} ÷ {tan (φ + α) + tan (φ + β)}

(4) Y = -2D {tan (φ + α) · tan (φ +
β)} / {tan (φ + α) + tan (φ + β)} As is apparent from the above-mentioned formulas 3 and 4, the parameter D
And φ are known, the two-dimensional coordinates of the designated position P can be easily calculated by measuring the pair of argument data α, β.

Finally, the procedure for measuring the deflection angle α will be described with reference to FIG. The same applies to the other deviation angles β.
The pair of linear light receiving surfaces 33A and 33B are arranged in parallel with each other with a predetermined space C therebetween, and the normal line S described above is provided.
It is orthogonal to R. In this example, the light beam detecting means is made of PSD for easy understanding. Light beam VR
The intersection between the light receiving surface 33A on the front side and the front side is represented by A, and the intersection between the same light beam VR and the light receiving surface 33B on the rear side is represented by B. These intersections A and B respectively represent the light receiving positions of the light spots separated from the light beam VR. Now P
A pair of differential signals output from the light receiving surface 33A of the SD
1, a2, the light spot position A is (a1-a2)
It is given by / (a1 + a2). Similarly, the light receiving surface 33B
Let b1 and b2 be the pair of differential signals output from
The light spot position B is given by (b1-b2) / (b1 + b2). Further, as is clear from the illustrated geometrical relationship, the argument α can be calculated from tan α = (B−A) / C. That is, it is possible to directly optically detect the deviation angle α of the light beam VR by measuring the pair of light spot positions A and B.

[0022]

As described above, according to the present invention, the beam direction of the laser light deflected by the deflecting means is directly detected optically. With this configuration,
The mechanical accuracy of the deflection means does not affect the measurement accuracy of position coordinates, and a highly accurate optical position measurement device is realized without using a motor or the like equipped with an expensive air bearing as the deflection means. The effect is that you can do it. Further, by using the pair of front-stage and rear-stage light spot position detecting means, there is an effect that it is possible to realize a high-precision optical position measuring device which is not affected by the axis deviation of the rotary reflecting mirror. Therefore, it is possible to use a piezoelectric vibration reflecting mirror or the like as the deflecting means instead of the rotating reflecting mirror, and there is an effect that an inexpensive and compact optical position measuring device can be realized. In particular, recently, there is an increasing demand for a transparent digitizer to be mounted on the front surface of a large-sized television, and there is an effect that it is possible to economically realize a small-sized optical position measuring device which is optimal for constructing an electronic conference system or the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of an optical position measuring device according to the present invention.

FIG. 2 is a plan view of a light source unit incorporated in the optical position measuring device shown in FIG.

FIG. 3 is a side view of the light source unit.

FIG. 4 is a geometrical optical diagram showing a designated position coordinate calculation procedure of the optical position measuring device according to the present invention.

FIG. 5 is likewise a geometrical optical diagram showing a procedure for measuring a deflection angle of a light beam.

FIG. 6 is a schematic view showing a conventional optical position measuring device.

FIG. 7 is a block diagram showing a configuration of a light source unit incorporated in a conventional optical position measuring device.

8 is a timing chart for explaining the operation of the conventional light source unit shown in FIG.

FIG. 9 is a schematic view showing another example of a conventional optical position measuring device.

[Explanation of symbols]

 1R, 1L Light beam emitting means 2R, 2L Deflection means 3R, 3L Light beam detecting means 4 Position indicating means 5 Measurement area 6 Calculation part 21 Rotating reflecting mirror 22 Motor 31A Pre-stage light spot position detecting means 31B Post-stage light spot position detecting means 32A Beam splitting means 32B Beam splitting means R Right light source unit L Left light source unit

Claims (4)

[Claims] 1. A light beam emitting means for emitting a light beam, a deflecting means for deflecting the light beam, a position indicating means for detecting that the deflected light beam has passed a designated position, and the detecting means. An optical position measuring device comprising a deflection amount detecting means for synchronously detecting the deflection amount of the light beam, wherein the deflection amount detecting means is interposed between the deflecting means and the position indicating means and is optically directly An optical position measuring device comprising a light beam detecting means for detecting a light beam direction. 2. The light beam detecting means includes a front light spot position detecting means for detecting a light beam spot position on the front side, and a rear light spot position detecting means for detecting the same light beam spot position on a rear side. The optical position measuring device according to claim 1, wherein the optical position measuring device comprises: 3. The optical position measuring device according to claim 1, wherein the light beam detecting means is composed of a CCD linear image sensor, a MOS linear image sensor or a PSD. 4. A two-dimensional light source unit consisting of a light beam emitting means, a deflecting means and a light beam detecting means is provided to detect a two-dimensional position designated by the position indicating means. Optical position measuring device.