JPH07128009A - Optical position measuring instrument - Google Patents

Abstract

PURPOSE:To provide an optical position measuring instrument with an improved environmental resistance. CONSTITUTION:The title instrument is provided with a light beam scanning part 1 for outputting parallel light beams which are scanned with a certain angular velocity around a certain origin 3 and a light reception part 4 with a light reception surface with a specific width (a) which is laid out opposite to it and where optical beams cross and a data processing circuit 8 calculates a distance (x) from the origin 3 of the light beam scanning part 1 to a light reception surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical position measuring device used for a positioning sensor, a length measuring scale, an XY encoder and the like.

[0002]

2. Description of the Related Art Conventionally, various position sensors such as capacitance type and optical type have been put into practical use. These conventional position sensors use a scale with graduations to detect a capacitance change between the opposing scales if the capacitance type is used, and to transmit or block light by the opposing scale if the optical type is used. The method of detecting the light and dark pattern is used.

[0003]

In the conventional position sensor, expansion and contraction due to temperature change of the scale, adhesion of dust, and the like cause measurement errors. It is an object of the present invention to provide an optical position measuring device adopting a new principle and having excellent environment resistance.

[0004]

An optical position measuring device according to the present invention comprises, firstly, a light beam scanning means for outputting a parallel light beam scanned around an origin at a constant angular velocity,
The light receiving means having a light receiving surface of a predetermined width across which the light beam from the scanning means arranged opposite to the scanning means and the output signal of the light receiving means and the width of the light receiving surface across which the light beam crosses the scanning means. And a calculation means for calculating the distance from the origin to the light receiving surface. Secondly, the optical position measuring device according to the present invention comprises a light beam scanning means for outputting a parallel light beam scanned around an origin at a constant angular velocity, and a scanning means arranged to face the scanning means. A reflecting means having a reflecting surface of a predetermined width for reflecting the incident light beam from the light beam in a direction parallel to the light beam, and a light receiving means arranged behind the light beam scanning means for receiving the reflected light beam from the reflecting means. And a calculating means for calculating the distance from the origin of the scanning means to the light receiving surface from the output signal of the light receiving means and the width across which the light beam of the reflecting means crosses.

[0005]

When the angular velocity for scanning the parallel light beam and the size of the light receiving surface for receiving the parallel light beam are predetermined, the rotation angle of the parallel light beam can be known from the time width of the light receiving signal. From this rotation angle and the size of the light receiving surface, the position of the light receiving surface, that is, the distance from the origin of the scanning means to the light receiving surface can be obtained by a simple geometrical calculation. The measuring device of the present invention does not use a scale in which conventional scales are engraved,
Further, since the light beam scanning means and the light receiving means can be hermetically sealed, the environment resistance becomes excellent. Also,
If a reflecting means such as a corner cube mirror that always reflects the incident light beam in the same direction as that is combined, the light emitting portion and the light receiving portion can be integrally formed, and the alignment becomes easy.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a principle configuration of a distance measuring device according to an embodiment of the present invention. The light beam scanning unit 1 includes a parallel light beam 2
Is scanned around the origin 3 at a constant angular velocity ω. A specific configuration example of the light beam scanning unit 1 will be described later. A light receiving section 4 for detecting the output light beam 2 is arranged opposite to the light beam scanning section 1. The light-receiving section 4 has a light-receiving element 5 whose light-receiving surface size is set to a. The light receiving element 5 may be, for example, a single photodiode, an array of small photodiodes, or
Two photodiodes arranged at a distance a may be used. The light receiving unit 4 is different from the light beam scanning unit 1 in that
One-dimensionally in the X direction of the XY coordinates shown in the figure, or XY
It is installed so that it can be moved in two dimensions.

The light beam scanning section 1 and the light receiving section 4 are sealed in cases 6 and 7, respectively. Although FIG. 1 shows that the light emitting end and the light receiving end are open,
In reality, a transparent window is provided. The output signal of the light receiving unit 4 is
It is sent to the data processing circuit 8 via a current-voltage conversion circuit, an amplification circuit, etc., which are omitted in the figure. A desired calculation is performed based on the signal detected by the data processing circuit 8,
The distance x from the origin 3 of the light beam scanning unit 1 shown in FIG. 1 to the light receiving surface of the light receiving unit 4 is obtained. The calculated distance data is displayed on the display device 9.

The principle of distance measurement in this embodiment is as follows. The angular velocity of rotation of the light beam scanning unit 1 is ω [ra
d / sec], and the time width of the output signal corresponding to the size a of the light receiving surface obtained by the light receiving unit 4 is t [sec], the rotation angle θ [rad] of the light source during this period is θ = ωt. . Then, the distance x is obtained by the following equation.

[0009]

## EQU1 ## x = a / tan (ωt)

FIGS. 2 and 3 show how the time width of the detected output signal changes according to the distance x. Since the rotational angular velocity ω of the light source is constant, the time width t of the output signal obtained on the light receiving surface of the size a is a function of the distance x,
It is represented by a curve as shown in FIG. As shown in FIGS. 2A and 2B, the cycle T of the output signal is constant, and the output signal time width changes like t1 and t2 according to the distance x. As can be easily understood from the above measurement principle, the device of the present invention is such that the closer the light beam scanning unit 1 and the light receiving unit 4 are to each other,
Since the rotation angle θ corresponding to the size a of the light receiving surface is large, the accuracy is high. Therefore, it is particularly effective as a proximity sensor or an origin sensor.

The output signal of FIG. 2 shows the case of one photodiode or photodiode array having a light receiving surface of size a, but as described above, the two photodiodes are separated by a distance a. It is also possible to arrange diodes. In this case, similar time data is obtained as the interval between the two output pulses obtained at the rising timing and the falling timing of the output signal time t1 or t2 in FIG.

FIG. 4 shows an example of the structure of the light source of the light beam scanning section. On the table 41 that is rotationally driven at the angular velocity ω,
Four laser diodes (or light emitting diodes) 42a to 42d are radially arranged, and collimator lenses 43a to 43d are arranged at respective output ends. In this case, the rotation center of the table 41 becomes the rotation center of the scanning light beam.

FIG. 5 shows another light source configuration example of the light beam scanning unit. In this example, a polygon mirror 51 that is rotationally driven at an angular velocity ω is used, and an output light beam of a fixed laser diode (or light emitting diode) 52 is collimated by a collimator lens 53 and reflected by the polygon mirror 51 to be a scanning beam. Is getting In this case, although the rotation center of the polygon mirror 51 and the rotation center of the scanning light beam are different, the rotation center of the scanning light beam is the origin 3 of the light source shown in FIG.

FIG. 6 shows another example of the configuration of the light beam scanning section. In this example, a light source in which a laser diode (or a light emitting diode) 61 and a collimator lens 62 that makes its output light parallel light is arranged on a table 62 that is linearly driven by a piezo piezoelectric element 64 whose one end is fixed is used. . Then, the output light beam that moves in parallel is converted into a convex lens 65.
Is converted into rotational movement to be a scanning light beam. In this case, the origin 3 of the scanning light beam shown in FIG.
Becomes the focus position of.

Although the one-dimensional measurement of the XY coordinates in the X-axis direction shown in FIG. 1 has been described above, by synchronizing the light beam scanning unit 1 and the light receiving unit 4, the configuration of FIG. Dimensional position measurement is also possible. The principle will be described with reference to FIGS. 7 and 8. Light receiving element 5 having a light receiving surface of size a
Are at coordinates (x, y) as shown in FIG. X
If the axis is used as the reference of the scanning light beam rotation angle and synchronous detection is performed on the light receiving element 5 side, the phase delay θ1 until the light receiving element 5 starts detecting the scanning light beam can be known. Further, the angle θ2 at which the scanning light beam scans the light receiving surface of the light receiving element 5
-.Theta.1 corresponds to the time width of the output signal as in the previous embodiment. That is, the output signal waveform of the light receiving element 5 is as shown in FIG. 8, and the angle θ1 = ω is obtained by the time t11 from the reference time of rotation.
t11 is obtained, and the angle θ2 = ωt12 is obtained from the time t12 obtained by adding the time width of the output signal to t11. On the other hand, the following relationship holds from FIG.

[0016]

[Formula 2] y = x tan θ1 y + a = x tan θ2

By transforming the above equation, x and y are respectively θ
It is calculated as a function of 1 and θ2 as follows.

[0018]

## EQU00003 ## x = a / (tan.theta.2-tan.theta.1) y = a tan.theta.2 / (tan.theta.2-tan.theta.1)

In the actual data processing, for example, a reference clock generator is used to generate a synchronization signal for the light beam scanning unit and the light receiving unit, and the times corresponding to the rotation angles θ1 and θ2 are obtained by counting the reference clocks. It is only necessary to perform the operation of Equation 3.

In the present invention, misalignment causes a large error. For example, when the light receiving surface is inclined by the angle φ, x in the equation 3 has an error component δx of the following equation.

[0021]

## EQU4 ## δx = a (1-cosφ) / (tan θ2-tan θ1)

Therefore, it is necessary to perform the alignment so that the error amount δx is below the resolution. Next, some design examples with specific numerical values will be given.

XY scale angular velocity for absolute measurement ω = 10π [rad / sec] Scanning range Θ = π / 2 [rad] Light-receiving surface size a = 6 [mm] When the clock is 2 MHz, the output signal period T = 50 [ msec] Measuring range (resolution) x, y: 0 mm (0.3 μm) to 500 mm (0.5 mm)

Absolute measurement scale angular velocity ω = π [rad / sec] Scanning range Θ = π / 30 [rad] Light receiving surface size a = 10 [mm] Clock 40 MHz, output signal period T = 40 [msec ] Measuring range (resolution) x, y: 110 mm (10 nm) to 1100 mm (10 μm)

High resolution position sensor for film thickness meter Angular velocity ω = π [rad / sec] Scanning range Θ = π / 30 [rad] Light receiving surface size a = 2 [mm] Clock 40 MHz, output signal cycle T = 40 [msec] Measuring range (resolution) x, y: 0 mm (0.3 nm) to 100 mm (0.3 μm)

High-speed position sensor for absolute measurement Angular velocity ω = 2000π [rad / sec] Scanning range Θ = π / 4 [rad] Light receiving surface size a = 5 [mm] Clock 40 MHz, output signal period T = 0 0.25 [msec] Measuring range (resolution) x, y: 0 mm (1.5 μm) to 100 mm (0.3 mm)

FIG. 9 shows the structure of a position measuring device according to another embodiment of the present invention. In this embodiment, a reflector 91 having a predetermined width is arranged in front of the light beam scanning unit 1 similar to that described in each of the previous embodiments, in front of which the light beam is sent. The reflector 91 is a planar or three-dimensional array of corner cube mirrors, each of which is formed by arranging three surfaces adjacent to each other so as to be orthogonal to each other. Instead, it has the property of reflecting at an angle equal to the incident angle. Immediately behind the light beam scanning unit 1, a light receiving unit 4 for receiving the reflected light beam from the reflector 91.
Are placed. In front of the light receiving unit 4, if necessary, f−θ
A lens 92 is arranged.

The principle of position measurement in this embodiment will be described with reference to FIG. First, if the f-θ lens is not used,
Assuming that the distance from the origin of the light beam scanning unit 1, that is, the light source position to the reflector 91 is D, the width of the light beam across the reflector 91 is A, and the time when the light receiving unit 4 detects the output signal is t, Letting ω be the rotational angular velocity of the beam, D = A / tan ωt. Therefore, the required distance is calculated from the time of the output signal detected as in the previous embodiment. The XY two-dimensional measurement can be performed by signal processing using a synchronization signal on the same principle as described in the previous embodiment with reference to FIG. 7.

When the position of the light receiving portion 4 can be detected and the f-θ lens 92 is used as shown in FIG. 9, the distance A'corresponding to the size A of the reflector 91 in the light receiving portion 4 becomes The scanning angle θ of the parallel light beam is obtained by θ = A ′ / f. Therefore, the required distance can be obtained by D = A / tan θ.

According to this embodiment, the light emitting portion and the light receiving portion can be integrally formed, and the number of parts can be reduced. Also, f-
If the θ lens is used together, the clock for synchronization becomes unnecessary. Furthermore, if the reflector by the corner cube mirror is configured three-dimensionally, alignment other than yawing becomes unnecessary and alignment becomes easy.

[0031]

As described above, according to the present invention, the optical position detection excellent in the environment resistance is achieved, in which the light beam is rotationally scanned at a constant speed and the position is obtained from the rotational angle by a simple calculation. A device can be provided.

[Brief description of drawings]

FIG. 1 shows the configuration of a position measuring device according to an embodiment of the present invention.

FIG. 2 shows a detection output signal of the embodiment.

FIG. 3 shows the relationship between signal detection time and distance in the same embodiment.

FIG. 4 shows a specific configuration example of a light beam scanning unit.

FIG. 5 shows another exemplary configuration of the light beam scanning unit.

FIG. 6 shows still another configuration example of the light beam scanning unit.

FIG. 7 is a diagram for explaining the principle of two-dimensional measurement.

FIG. 8 is a view for similarly explaining the principle of two-dimensional measurement.

FIG. 9 shows a configuration of a position measuring device according to another embodiment.

FIG. 10 is a view for explaining the measurement principle of the same embodiment.

[Explanation of symbols]

1 ... Light beam scanning unit, 2 ... Parallel light beam, 3 ... Origin, 4
... light receiving part, 5 ... light receiving element, 6, 7 ... case, 8 ... data processing circuit, 9 ... display device. 91 ... Reflector, 92 ... f-θ
lens.

Claims (2)

[Claims] 1. A light beam scanning means for outputting a parallel light beam scanned around an origin at a constant angular velocity, and a light beam of a predetermined width which is crossed by the light beam from the scanning means arranged opposite to the scanning means. A light receiving means having a surface; and an arithmetic means for calculating a distance from the origin of the scanning means to the light receiving surface from an output signal of the light receiving means and a width of the light receiving surface traversed by the light beam. Optical position measuring device. 2. A light beam scanning means for outputting a parallel light beam scanned around an origin at a constant angular velocity, and an incident light beam from the scanning means arranged facing the scanning means in parallel with the light beam scanning means. Direction, a reflecting means having a reflecting surface of a predetermined width, a light receiving means arranged behind the light beam scanning means for receiving the reflected light beam from the reflecting means, an output signal of the light receiving means and the reflection An optical position measuring device, comprising: a calculating unit that calculates a distance from an origin of the scanning unit to the light receiving surface based on a width across which the light beam of the unit crosses.