JPH06323872A - Zero point position detector - Google Patents

Abstract

PURPOSE:To allow easy formation of a zero point detection pattern without requiring any etching by forming the zero point detection pattern or the periphery thereof into a diffused surface. CONSTITUTION:First and second light beams 1, 2 are partially reflected on a half mirror 3 and impinge normally on a scale 4. The scale 4 moves in the arrow direction and when diffused surfaces 51, 52 approach points P1, P2, the diffused surface 51 arrives at the position P1 at first and thereby the light beam 1 reflected on a reflective surface 7a is scattered on the diffused surface 51 thus reducing the reflected light 1' impinging on a light receiving element S1. When the diffused surface 52 arrives at the position P2, the light beam 2 is scattered on the diffused surface 52 thus reducing the reflected light impinging on an element S2. Signals from the elements S1, S2 have a phase shift and delivered on a signal line L to a zero point detecting means 6. The means 6 generates a signal representative of the zero point of scale 4 immediately upon matching of input signal level thus detecting the zero point of the scale 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zero point position detecting device for an encoder used in the fields of industrial machine tools and measuring machines for measuring the movement and rotation of an object.

[0002]

2. Description of the Related Art Conventionally, an encoder has been used as a displacement sensor for detecting a position and an angle in NC machine tools and the like. Further, this type of encoder is required to have high resolution, high accuracy, and low cost. Depending on the displacement of the diffraction grating, the recording density of the diffraction grating used as the scale of this encoder is set to several microns / pitch, a pair of diffraction lights generated by this diffraction grating are extracted and interfered, and the interference light is photoelectrically converted. Several high-resolution and high-precision displacement measuring devices capable of obtaining periodic signals have been proposed.

The zero point position detecting device of the scale incorporated in this device is required to have detection resolution and accuracy. Therefore, as shown in FIG. Scale 4 with 2 formed
A first light flux 1 and a second light flux 2 which are condensed on the scale 4, and a first photoelectric conversion means S1 which photoelectrically converts the first light flux 1'reflected by the scale 4 and outputs a first signal, Second photoelectric conversion means S2 that photoelectrically converts the second light flux 2'reflected by the scale 4 and outputs a second signal, and a first signal output from the first photoelectric conversion means S1 and the second photoelectric conversion means S2. The zero point detecting means 6 outputs a signal indicating the zero point position of the scale in response to the coincidence of the level of the second signal, and the zero point position detecting patterns 5-1 and 5 are provided.
-2 was a reflective surface or a translucent surface.

[0004]

Since the conventional zero point position detecting device is constructed as described above, if the etching is performed after the metal film is deposited, the zero point position detecting patterns 5-1 and 5 are obtained.
A -2 reflective or transmissive surface can be easily made.
However, there is a problem in that it is difficult to provide the reflective surface or the translucent surface when a manufacturing method without etching, for example, a replica method is used.

An object of the present invention is to obtain a zero point position detecting device which solves the above problems.

[0006]

According to the invention of claim 1, a scale on which a zero point position detection pattern is formed by shifting the positions in the front and rear of the moving direction, and a first light flux and a second light flux are provided on the scale. An optical system for condensing, a first photoelectric conversion means for photoelectrically converting the first light flux reflected by the zero point position detection pattern and outputting a first signal, and a second light flux reflected by the scale for photoelectric conversion. Position detecting device having second photoelectric conversion means for outputting a second signal and zero point detecting means for outputting a signal indicating the zero point position of the scale in response to the coincidence of the levels of the first signal and the second signal. In the above, since the zero point position detection pattern is a diffusion surface or a portion other than the zero point position detection pattern is a diffusion surface, if applied to a replica scale, a low cost and highly accurate zero point position detection pattern can be obtained. Over emissions can be formed.

According to the second aspect of the present invention, a scale having a zero point position detection pattern formed by shifting the position in the front-back direction and an optical system for converging the first light flux and the second light flux on the scale. A first photoelectric conversion unit that photoelectrically converts the first light flux reflected by the zero point position detection pattern and outputs a first signal; and a second light flux that photoelectrically converts the second light flux reflected by the scale and outputs a second signal. Second photoelectric conversion means,
In a zero point position detecting device having a zero point detecting means for outputting a signal indicating the zero point position of the scale in response to the coincidence of the levels of the first signal and the second signal, a zero point position detecting pattern is a diffraction grating or the zero point. By forming a portion other than the position detecting pattern as a diffraction grating, the zero point detecting pattern can be formed at low cost and with high accuracy.

[0008]

【Example】

Example 1. Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view showing an embodiment of the invention of claim 1. In FIG. 1, reference numeral 1 is a first light beam condensed on the scale 4, 2 is a second light beam condensed on the scale 4, and 3 is an optical system for converging the first light beam 1 and the second light beam on the scale 4. Half mirrors, 51 and 52 are first and second diffusing surfaces forming a zero point position detection pattern, and 7a is a zero point position detection of the scale 4 irradiated with the first light flux 1 and the second light flux 2. In a portion other than the pattern for use, a reflecting surface, 1'is reflected light of the first light flux 1, 2'is reflected light of the second light flux 2, and 6 is a scale based on signals from the light receiving elements S1 and S2 as light ray converting means. 4 is a zero point detecting means for outputting a signal indicating the zero point position.

The first light flux 1 and the second light flux 2 are partially reflected by the half mirror 3 and are vertically incident on the scale 4. The scale 4 receives a driving force from a driving means (not shown),
Move in the direction of the arrow, and the diffusion surfaces 51 and 52 are located at the positions P1 and P2.
When approaching, the diffusing surface 51 reaches the position P1 first, so that the first light flux 1 which has been reflected by the reflecting surface 7a until then is dispersed by the diffusing surface 51 and is incident on the light receiving element S1. A decrease occurs. Subsequently, when the diffusing surface 52 reaches the position P2, the second light flux 2 is dispersed on the diffusing surface 52 and the reflected light 2'which is incident on the light receiving element S2 is reduced.

The signals from the light receiving elements S1 and S2 are signals whose phases are deviated from each other, and are respectively input to the zero point detecting means 6 via the signal line L. The zero point detecting means 6 generates a zero point signal indicating the zero point position of the scale 4 at the moment when the levels of these input signals coincide with each other, and this means that the zero point position of the scale 4 is detected.

Example 2. FIG. 2 is a schematic view showing an embodiment of the invention of claim 1. In FIG. 2, 1 is a first light beam condensed on the scale 4, 2 is a second light beam condensed on the scale 4, 3 is a half mirror, and 53 and 54 are first zero-point position detecting patterns. And a second reflecting surface, 7b is a diffusing surface of a portion other than the zero point position detection pattern of the scale 4 on which the first light flux 1 and the second light flux 2 are irradiated, and 1'is the reflected light of the first light flux 1. 2'is reflected light of the second light flux 2, S1 and S2 are light receiving elements, and 6 is light receiving elements S1 and S2.
It is a zero point detecting means that outputs a signal indicating the zero point position of the scale 4 based on the signal from.

The first light flux 1 and the second light flux 2 are partially reflected by the half mirror 3 and are vertically incident on the scale 4. The scale 4 receives a driving force from a driving means (not shown) and moves in the direction of the arrow, and when the reflecting surfaces 53 and 54 approach the positions P1 and P2, the reflecting surface 53 reaches the position P first. The first light flux 1 which has been dispersed on the diffusing surface 7b until then is reflected on the reflecting surface 53 and the reflected light 1'incident on the light receiving element S1 increases. Subsequently, the reflecting surface 54 reaches the position P2, the second light flux 2 is reflected by the reflecting surface 54, and the reflected light 2'incident on the light receiving element S2 increases.

The signals from the light receiving elements S1 and S2 are signals whose phases are shifted from each other, and are input to the zero point detecting means 6 via the signal lines L, respectively. The zero point detecting means 6 generates a zero point signal indicating the zero point position of the scale 4 at the moment when the levels of these input signals coincide with each other, and this means that the zero point position of the scale 4 is detected.

Example 3. FIG. 3 is a schematic view showing an embodiment of the invention of claim 2. In FIG. 3, 11 is a scale 1
4 is a first light flux condensed on the scale 14, 12 is a second light flux condensed on the scale 14, 13 is a half mirror as an optical system for condensing the first light flux and the second light flux on the scale 14, and 71 and 72 are A diffraction grating forming a zero point position detection pattern, 17a is a reflecting surface that is a portion other than the zero point position detection pattern of the scale 14 on which the first light flux 11 and the second light flux 12 are irradiated, and 11 'is the first light flux 11. Reflected light, 12 '
Is the reflected light of the second light flux 12, S1 and S2 are the reflected light 11 ',
A light receiving element as a photoelectric conversion element for receiving 12 ', 16
Is a scale 1 based on signals from the light receiving elements S1 and S2.
4 is a zero point detecting means for outputting a signal indicating the zero point position.

The first light flux 11 and the second light flux 12 are partially reflected by the half mirror 13 and are vertically incident on the scale 14. The scale 14 receives a driving force from a driving means (not shown) and moves in the direction of the arrow, and when the diffraction gratings 71 and 72 approach the positions P1 and P2, the diffraction grating 71 moves to the position P first.
Since it reaches 1, the first light flux 11 that has been reflected by the reflecting surface 17a is diffracted by the diffraction grating 71 and the reflected light 11 'that enters the light receiving element S1 is reduced. Then, the diffraction grating 72 reaches the position P2 and the second light flux 12 is emitted from the diffraction grating 7
The reduction of the reflected light 12 'diffracted by 2 and incident on the light receiving element S2 starts.

The signals from the light receiving elements S1 and S2 are signals whose phases are shifted from each other, and are input to the zero point detecting means 16 via the signal lines L, respectively. The zero-point detecting means 16 generates a zero-point signal indicating the zero-point position of the scale 14 at the moment when the levels of these inputs match, and this means that the zero-point position of the scale 14 has been detected.

Example 4. FIG. 4 is a schematic view showing an embodiment of the invention of claim 2. In FIG. 4, 11 is a scale 1
4 is a first light flux condensed on 4, a second light flux is condensed on the scale 14, a 13 is a half mirror, and 73 and 74 are a first reflection surface and a second reflection which form a zero point position detection pattern. Surface 17b is the first light flux 11 and the second light flux 1
2 is a diffraction grating of a portion other than the zero point position detection pattern of the scale 14, 11 'is reflected light of the first light flux 11, 12' is reflected light of the second light flux 12, 16 is reflected light 1
The zero point detecting means outputs a signal indicating the zero point position of the scale 14 based on the signals from the light receiving elements S1 and S2 which receive 1'and 12 '.

The first light flux 11 and the second light flux 12 are partially reflected by the half mirror 13 and are vertically incident on the scale 14. Since the scale 14 receives the driving force from the driving means (not shown) and reaches the direction P1 in the arrow direction, the first light flux 11 that has been diffracted by the diffraction grating 17b until then is reflected by the reflecting surface 73 and is received by the light receiving element. An increase in the reflected light 11 ′ incident on S1 occurs. Then, the reflection surface 74 reaches the position P2, the second light flux 12 is reflected by the reflection surface 74, and the reflected light 12 'that enters the light receiving element S2 increases.

The signals from the light receiving elements S1 and S2 are signals whose phases are shifted from each other, and are input to the zero point detecting means 6 via the signal lines L, respectively. The zero-point detecting means 6 generates a zero-point signal indicating the zero-point position of the scale 14 at the moment when the levels of these input signals match, and this means that the zero-point position of the scale 14 has been detected.

[0021]

As described above, according to the first aspect of the present invention, the zero point position detecting pattern or the periphery other than the zero point position detecting pattern is formed on the diffusing surface. According to the second aspect of the invention, the zero point position detecting pattern. Alternatively, since the surroundings other than that are made to be a diffraction grating, the zero point position can be detected by means other than the reflecting surface and the transmitting surface, and the zero point position detecting pattern can be easily formed without etching. As a result, by forming the zero point position detection pattern by applying the replica scale, it is only necessary to process the pattern into the mold, so that an inexpensive and highly accurate zero point position detection device can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a zero point position detection device according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a zero point position detecting device according to a second embodiment of the present invention.

FIG. 3 is a perspective view showing a zero point position detection device according to a third embodiment of the present invention.

FIG. 4 is a perspective view showing a zero point position detecting device according to a fourth embodiment of the present invention.

FIG. 5 is a perspective view of a conventional zero point position detection device.

[Explanation of symbols]

 1, 11 First luminous flux 2, 12 Second luminous flux 13 Half mirror (optical system) 4, 14 Scale 5a, 5b, 15a, 15b Zero point position detection pattern 6,16 Zero point detecting means 51, 52, 7b Diffusing surface 71, 72,17b diffraction grating

Claims (2)

[Claims] 1. A scale in which a zero point position detection pattern is formed by shifting the position in the front-back direction of the moving direction, an optical system for converging the first light flux and the second light flux on the scale, and the zero point position detection pattern. A first photoelectric conversion means for photoelectrically converting the first light flux reflected by and outputting a first signal, and a second photoelectric conversion means for photoelectrically converting the second light flux reflected by the scale and outputting a second signal. A zero point position detecting device having zero point detecting means for outputting a signal indicating the zero point position of the scale in response to the coincidence of the levels of the first signal and the second signal, the zero point position detecting pattern or the zero point position detecting A zero point position detecting device, characterized in that a portion other than the working pattern is a diffusion surface. 2. A scale on which a zero point position detection pattern is formed by shifting the position back and forth in the moving direction, an optical system for converging the first light flux and the second light flux on the scale, and the zero point position detection pattern. A first photoelectric conversion means for photoelectrically converting the first light flux reflected by and outputting a first signal, and a second photoelectric conversion means for photoelectrically converting the second light flux reflected by the scale and outputting a second signal. A zero point detecting device having a zero point detecting means for outputting a signal indicating a zero point position of the scale in response to the coincidence of the levels of the first signal and the second signal, the zero point detecting pattern or the zero point position detecting pattern A zero-point position detection device characterized in that a diffraction grating is used other than the pattern.